I'm with Gearbanger and WhiteStang on this one. The sound difference isn't that much with a good aftermarket X (or H) pipe with low restriction, high flow cats as opposed to a stinky O/R X. I don't have emissions testing here either, but we had a pair of
Magnaflow cats welded into my wife's O/R H on her 01 GT...the sound difference was minimal, the power difference wasn't even noticable, but the smell difference was huge!
My 02 GT is getting a catted X or H...still can't decide which one...but I'm poor right now, so it really doesn't matter much! I'm leaning toward the
www.pypesexhaust.com catted X (the same thing that MustangTuning sells)
X pipe for stock manifolds/shorties - $315 catted, $392 catted & ceramic coated (sweeeet!)