[98SteedaGT]

If you didn't change your O2 Sensors when you did this, you may want to look in to it. I have always bought 4 new senors when changing out the exhaust like that. I have a 98GT with that same H-Pipe and never had any problems with it. I only started having problems here after I did the TA/MAF/Underdrives at the same time. I have noticed that I have to run Texaco93 in my car, if I don't the MIL comes on. I know it sounds odd, but I have done it over and over.. and no matter what other type of grade/make gasoline I put in the car, it will always set off the computer about 5mi down the road. Only the Texaco93 will go tank after tank w/o MIL coming on... It's not just that one station, it's any station with Texaco93... I don't know what they do differently, but; it's the only gas my car will burn now and not complain about..... go figure... I think it's because my Mustang is powered by a Mac computer, not and Intel :-D hehe