papaindigo wrote:
Personally I would not remove the muffler and some who have report annoying noise on the other hand some like it removed. If you actually look at the exhaust system piping there are 3 "choke" points - 1) the smallest which cannot be removed is the turbo housing at the exhaust pipe connection which IIRC is maybe slightly over 2" in diameter; 2) the bend in the exhaust pipe just below the firewall which like varies in diameter from vehicle to vehicle; and 3) where the pipe IIRC necks down a bit just in front of the muffler. If you want to open things up get a 2.5" muffler like a Magnaflow Muffler #12226 and install it along with a bit of exhaust pipe to remove that constricted area right near the muffler.
You can "gut" the cat and leave it on or you can remove the cat. If you remove the cat put it on the shelf in case the vehicle ever winds up in an area where it won't pass inspection without at cat or at least a cat housing.
I removed my Muffler and it is louder. Its not terrible, but I noticed no improvement in anything so its not really worth it in my eyes. A magnaflow is probably the best idea.
Oh, the exhaust also necks down through the flange between the cat and muffler.