I am planning on doing a gundo hack and have been thinking about going with FisterD. However, I have a local guy who said he can do it for $300 and that includes the cans so I can keep my originals. He uses 1.5" pipe. SOme folks do 1.25", I think Fister does 2". So my question is what is the difference between the pipe sizes used for the hack? What is the impact to sound? Drone? and anything else?

 

Go with Fister. He is the master of this process.

 

I used 2" .

 

I used 1.75", no drone, sounds great.

 

Fister uses 1.75. I've tried 1.5 at a local shop. Both do not drone and 1.75 sounds a little louder. If I were to do it again, I would have gone 2 and I like loud.
I have the 1.75 modified by fister sitting in the garage as I have gone fabspeed supercups. Maybe I'll let mine go...but you can't beat your local guy if he's doing that including the cans.

 

I did 1.75" by my local shop. I like loud at WOT and I was not impressed. It was louder at startup and at WOT, but only approx. 50% louder. If I did it again, I would do 2.25" since I like louder. However, there was no drone whatsoever.

 

My 2" has no drone and sounds good. If in fact you like it "louder" this mod is not the way to go. At over 2" you start to loose back pressure which lowers low end tourque.
If "loud" is what you are looking for, Fabspeed cat bypass pipes with your muffler mod.

 

just did my today with 1.75 it cost me $ 300 and sounds great and no drone