i own a 98 gt, and recently my check engine light came on. then i noticed that when i punched it, it started to stutter at around 3500-4500 rmp. it does it in all the gears. i added injector cleaner and fuel additives, and the check engine light went out, but it still stutters, not as much as it did before but its still there. my car was in the body shop so im going to pull my fuel filter and clean it . any other ideas?