I would also be interested in seeing the differences between my setup and a 3" turbo-back exhaust w/ race cat or not cat... maybe I'll get an Evo buddy of mine to let me switch out exhausts during dyno testing... but then I'd have to pay for twice the dyno time, rawr...

Only thing I've noticed from the traditional 3" TBE setups is my turbo spools a bit faster... as far as anything else, I dunno unless I'm on the dyno to get solid results.