Gordy is here now!!!! (straight from Seattle WA)
Here is the scoop. I had 3" straight mandral bent pipe with the cat elimintaed and a high flow camaro magnaflow muffler. I noticed a small drop in low end torque, but it opened up nicely at higher speeds. As Jason stated though, I did have enough low end HP to lay some tracks (http://www.mnbonnevilleclub.com/misc//newtoy.mpg
). My recommendation is use a slightly smaller pipe and keep high flow components in it such as high flow cat and muffler. Anything bigger / more free flowing would be a waste IMO.