Well, today was the day after the install, the day for "sobering up" from the awesomeness of the new pipe, and to assess the problems...
1)My check engine light came on, just like 98BLKHRSE said. I installed the two MIL peices just as instructed. I connected them to the rear o2 sensors. I hooked them up properly, hooking each in the middle of the clips, just like instructed. So what gives?

Also, I seem to be getting worse gas mileage, which could be related to the CEL trip.
2)The rasp. It seems worse then yesterday. Whenever I get on it, in 1st-3rd gear, I get nasty rasp. It doesn't matter what RPM either, it rasps everywhere 2000rpm+. But when I put the car in nuetral and revv it, there is only a LITTLE bit of rasp at 3500rpm, but overall theres really none while being revved. The rasp sounds like a metallic rattling/vibration. I theorize it could be the metal washers that came with the pipe, that was used in bolting the pipes together, which could be vibrating against the metal pipe or something. I like a little rasp, which is part of the reason I went with the X, but in some instances it gets out of hand. Aside from the rasp, the sound is really awesome, it gives an awesome angry howl that I haven't heard on any other car. Would wrapping the pipe in header wrap help anything? Any other thoughts?