OK with my OEM exhaust I have the 400 Cell rear Cats drilled out and the front 200 Cell cats replaced with 100 Cell Race Cats. My question is with an OEM TT exhaust has anybody ever removed BOTH sets of Cats and run totally Cat free as externally nobody can tell

 

That's my current setup. Gutted cats with a stock exhaust. It's stock quiet, but it smells so you can tell there are no cats.

 

I don't think those 100 cats are hurting you in restrection, especially with the stock muffler plumbing..

 

I would agree, plus I have seen a test where a gutted cat didn't flow as well as a high flow cat. Basically as the exhaust flows into the larger diameter chamber where the cat has been gutted, it creates turbulence causing a reduction in flow.

Later, Steve

 

Yes you are right about gutting cats and leaving that empty chamber.

 

what about replacing the cats with straight pipe?

 

That would be a better option. Now you have to deal with the rear O2 sensor causing a fault code; although an ECU mod will fix it and I've read you can shim the rear sensor with some success.

 

+1. Done it. The smell is not too fitting either.

 

You should modify the muffler now to get a power gain and not worry about the 100 cell cats..Just my opinion..

 

Can anyone tell me what the cell count is of the stock cats? This thread says 200 cell for the primaries (ones closest to the turbo) and 400 for the secondaries but not sure that is correct.

Thanks!

EDIT: Found this thread that states there are two 300 cell cats which makes sense as I heard people saying the cats are 600 cell.

https://www.6speedonline.com/forums/...s-cutaway.html