Quote Originally Posted by gtpinsc View Post
let me kinda give u some insight on this car... i bought it about 2 years ago, i went through 3 trannys in that time. dealership came to find that i had a 99 pcm in a 2002. so they flashed it back to stock. im pretty sure this car was demodded from 3.25. also pretty sure it has autolite 104's in it. my only mods are CAI and a downpipe. if those 104's are still in would they perform ok with a stock tune?
typically, 104's are used on 3.4 setups, and below that 103's etc etc...

You could try running stock equivalent plugs. You say it feels sluggish at times, How old is the catalytic converter on the downpipe? It might be prairie dogging.