But that is one of the friggin longest posts I've ever read. After reading all that, I can't really remember what the problem was. LOL. I know one thing though, you're getting RIPPED paying 80-90 bucks for installation. Give me a cat and a 6-pack, and you've got urself an installed cat.

Every 15K miles, the check engine light comes on as a maintenance thing, but I don't know if that may be it. Here's what to try and do:
1) Have key in ignition "off"
2) Hold the odometer push button thing for about 25 seconds, and then while still holding it, start the car.
3) If it doesn't go off, try it again.