Only problem I had with my cat'ed UPR X-pipe was that they welded the cats into place WAY too far back (by design) and they won't clear the transmission crossmember. It's caused me no end of headaches from Day 1, between scraping on speed bumps to rattling noises at WOT. I wound up having to notch the crap out of my crossmember just to make the stupid thing clear without rattling/banging under hard throttle.
As far as fitment, I'm not sure if it has to do with the X-pipe so much as the muffs I put on, but after I upgraded to my Violator mufflers, I had a helluva time fitting the things in there because of length differences - they were at least an inch farther back versus the Dynomax Super Turbos I took off, if not two inches longer - and I'm still scraping the crap out of everything because my darned hangers are so far out at their limits that they pop out of the rubber mounts and start wiggling their way down 'till they scrape on flat pavement. I think this has a lot to do with the fact that UPR is one of the few that doesn't utilize the transmission crossmember hangers; sure, it makes the install go a lot easier, but over time it appears that the center section starts to sag (even with everything tight as hell) and you have to keep jacking it back up and re-tightening everything to keep it from looking ghetto and scraping on everthing.
If I'd had the dough, I probably would've sprung for a Magnaflow X-pipe or even a plain ol' Catco H-pipe. True, I love the sound of my setup to death, but the headaches involved with the crappy fitment just don't justify the savings in cost and ease of install.
I'm on the verge of ordering a pair of 180* mandrel-bent U-turns and a couple of 90* elbows to just go with a side-exit exhaust. I'm so frickin' sick of fighting these stupid tailpipes - on top of all the other fitment issues with everything else in my exhaust setup - that I couldn't care less if I've got aluminized or stainless sticking out from under my car.
