I have a 98 GT...automatic....i think the idle is way too low its like 550-600 in drive i would like it to be higher it has a BBK TB i adjusted the idle screw a little but it didnt seem to help what else can i do thanks....
Altering the TB set screw does not work because the PCM is still attempting to adjust the idle to the same point using the Idle Air Controller (IAC). If you continue to add more idle air using the TB set screw, once all of the IAC adjustment has been used up, the idle will increase. However, the first time the weather changes, you will be stuck with a high idle condition.
The idle mentioned in the post sounds normal to me. But if you insist on increasing the idle, get yourself a tuner. Modifing the PCM is the only way that it will really work.