Ok, so my Check engine has been on since I bought my Stang. I had it checked out before I bought it, and it said that it was "cats performing below normal". Well, I can live with that. I would just get a new cat later down the line. when I was getting my gears put in from one of my buddies, he noticed I only had 2 cats from the Flowmaster setup the previous owner put in. He said that my year Stang usually had 4. Would this be causing the light to pop on? Would there be any way of "tricking" the computer to think that there are 4 cats? Any help would be great! Thanks!