I have plenty of clearance around the header and collectors but my ORY hits the front drivshaft when it crosses underneath it. I took a bat and huge rubber mallet to it for about a 1/2 inch of clearance. I don't think it a big enough dent to affect flow

 

yeah my y-pipe used to hit the front driveshaft a tiny bit, but it has since ground down and now clears fine. i hope it didn't wear a hole in the y-pipe. haha.

 

Crap! I hadn't thought about that?!