Well, probably most experienced people here already know all (most) of that, but if any amateurish DIYers will try to do it - consider following below.

PRIOR to doing anything - decide right up front if you go with Fabspeed mufflers or stock ones. Fabspeed cat pipes that connect to mufflers HAVE TO BE CUT 2" or so to fit into setup with stock mufflers. And should not be cut if you go with Fabspeed mufflers. I have discovered it in the middle of process and had to call Alex to figure out this puzzle.

Somebody here stated that it`s like 1 hour top job to replace cats - well, I started 9am and now it is 2pm, still not done. why?

First of all - Porsche apparently uses regular simple _iron_ nuts and bolts on all exhaust parts. What does it mean for you if your car is more than 2-3 years old? Nothing good, really. Everything rusty like hell. I was pre-soaking it all for 3 days in WD40 - it helped very little.
So consider to have complete replacement set of all bolts and nuts - Fabspeed generously provided gaskets for headers and new bolts/nuts for headers, but for other brackets - you may need new ones too.

So, for me this DIY meant 4 completely broken off bolts from cats/headers link - 2 lower ones on both sides, both upper ones survived. Thank You Mother Of God they did put such a lousy bolts there - I have no clue what would I do if I rounded nuts over there. Especially upper ones. To reach em you need 2 extension bars and connector.

1 completely rounded nut on right side bracket that presses cat and muffler pipes together - had to be freaking hammered like crazy to get it splitted in half (and neighbors were delighted to see crazy guy who hammers 'almost brand new' Porsche like a crazy maniac) - because normal nut splitter does not fit into that miserably small opening under that bracket where this nut sits. Very unpleasant process.

So, muffler removal is also pretty paunful thing as you have to unscrew 3 nuts from inside of very little space because some IDIOT on manufacturing line apparently decided not to turn over 2 long bolts that were so ingeniously designed to hang those mufflers on. 5 minute muffler removal job converted into 30 minutes at least for each side.

Now, when you need to take of this stuff - proper sequence of actions should be:

1. take off airbox.

2. unplug oxygen sensors on both sides, both. After that tear off black plastic connector (not a wire!) from its plastic holder and then drop down to cats all 4 wires with connectors on them. Do not even try to unscrew oxygen sensors while cats are on car - it is waste of time, you will not succeed.

3. Get under the car. It is enough to put it on racks like Rhino 12000 or so.
Then remove metal rods in front of mufflers - 10mm bolt on top, special screw below.

4. Help you God - undo those brackets that do hold cat and muffler pipes together. 4 13mm nuts. Use gator heads if you have em. DO NOT overpush as if you round `em - that will be FUN.

5. As muffler pipe is free and your car is stock - do not even try to unscrew those 2 conviniently looking nuts on bottom of muffler hangers - you need to get into inside space of inside muffler wall and undo those 3 nuts there. You`ll need 13mm head, ratchet and extension bars and that bendable extension bar that allows you to have an angle. Passenger side is much more difficult to do - less space there and a pipe that obstructs access.
But in time you`ll get mufflers off.
When you get them off - unscrew bolts from those hangers, put plates back on car, screw those 3 sorry nuts back, and put damn bolts back but in REVERSE position - nut up front, bolt head down. WHAT IDIOT on Porsche undid this great design I do not know but GOSH was it annoying...
Then take off muffler tips.

6. Cats. you still have oxygen sensor on em - be EXTRA careful not to twist cats and brake off sensors - it will be extra expense and delay. I did not brake `em.
So, as mufflers are gone go ahead and loosen (but do not take off) up both brackets that hold cats in place - CAREFULLY proceed with undoing nuts between headers and cats. Be ready to see broken off bolts. Now, as for people who want headers replaced on an old car - my assessment is - DO NOT RECOMMEND that. RUSTY!!!! If average car is in same shape as mine 2006 car is - those bolts on headers are now a part of an engine block. It is not a DIY job to try to fight them. So, headers will stay.

So as you loosen up brackets on cats - proceed with cat on a left side - you can see one big barrel sort of sits below another - this is first one to be removed. As you got it disconnected from header - carefully looking at oxygen sensor remove bracket and twist cat down - it will barely go but will get off. There are very little space there between rear bumper and other cat. After cats are on ground carefully unscrew oxygen sensors, note where black one sits and blue one sits and screw them into new cat.

So generally, that is it. mounting up new cat took probably whopping 10 minutes or so. Then connected back oxygen sensors, all wires went into proper holders, etc, aibox on - end of story.


Tomorrow Ill get new Fabspeed mufflers to try em on - I got a promise of 'sound warranty' from Alex - KUDOS - so I`ll see how loud it will get, if not too loud - I`ll keep em on, if it will not be tolerable - I will put stock ones on.

Tried to start car - uau, that was _some_ sound. Nice, but completely not acceptable for street car. That is probably now muffler bypass sounds I guess.

 

Wow - your post makes this sound so difficult.

Mufflers are pretty easy to remove on my car - 30 minutes total.

Cats are a bit tougher, but not much. I didn't need to remove the airbox - the O2 sensors simply unscrew.

Porsche clamps are pretty good and mine have held up with zero rust.

Are you saying you are running your car with just cats, no mufflers? Bet that sounds badass!

 

It is not difficult to remove `em perhaps if all bolts and nuts are brtand new and oiled.
When it is all rusty - you do not really have enough leverage there to undo `em. So it becomes quite difficult.

As well as to unscrew old O2 sensors - I needed 22mm wrench with extension to let it go. It was freaking almost soldered to the cat.

I was sort of ready for all this, any old exhaust work is a challenge. I just did not expect that ALL nuts/bolts there will be simple cheap iron ones.
And as a warning - if anyone assumes it is a 1 hour of billable time in a shop to get this done on an old car - think more like 4-5 hours. Splitting that freaking nut alone probably took 90 minutes or so. So, $120 per hour, do your math.
Not to mention that if mechanic in shop will not be able to fit a hydraulic nut splitter over that nut (and he WILL NOT be able to do that there, beleive me) - most likely he will turn you over as he likes himself better than sitting there smashing hammer on a chisel for 2 hours straight.

Yes, BTW, I did not took off wheels nor bumper as some other post on renntech suggested. And nothing of that is 'difficult'. It is just time consuming.

 

Thanks for sahring your ordeals and tips. Will keep these in mind when I do mine. Rep point for your hardwork .

 

On this alone - there is no space above cats to properly fit wrench nor you have leverage to turn that wrench. Plus just unscrewing sensors and heaving them there without disconnecting them you will over-twist wires - not good, plus what even worse you can get dirt and oil or even bend sensor surface - all that will damage sensor. It is much safer to work with sensors when you got cats on a ground.

 

Managed to remove O2 sensors with no problem. I'm simply saying it is not necessary to remove the airbox - even though I certainly recognize the merits of safety and caution, as you've pointed out.

 

Thanks for sharing the details. Sounds like fun stuff. I can't wait to attempt changing my headers as I'm sure I'll encounter the same thing...rust! Looking under my car at the stock setup makes me think Porsche cut some corners here in the hardware department.

 

It is all doable but just be extra careful with those headers bolts. If you will round or break off head from one of those - it will result in very big $$$ as you`ll have drill out broken bolt parts from the engine block, then redo it, well, it is pain. I did it once so I know.

If it will not go easily after some reasonable force applied then perhaps only way is to torch it until cherry red and then as it will just cool down from that color try to get it off, but, well, I would not do it to my engine, it is just beyond of my DIY comfort zone.

 

My car was only 3 mos. old when I did the exhaust so I didnt have any issues of rusted bolts. That being said I installed the whole exhaust system, headers, cats and mufflers in 3.5 hrs. with the car on tall Yellow Page phone books which I just backed the car onto. I didnt have to remove the airbox. Didnt seem to be necessary to me..The mufflers were the longest part of the install as you said the 3 bolts per side of the mufflers are kind of a pain. The reason why those long bolts are installed the way they are is incase the nut loosens and falls off that long bolt will stay inplace therefore keeping the muffler in place. I know Raffi (long time board member)installed that long bolt upside down as it made a muffler change so easy now. I didnt want to do that as I was afraid if it ever did come off (the nut) that my luck one of the mufflers would end up coming off.Glad you persisted and got it done though...usually when I am dealing with a car 2 years or older I like to have an impact wrench handy just in case of rusted bolts.Dave

 

Do it quick before rust sets in....moral of this story..