So I have 2 problems Im lookin for help with 1) I've spent a little over $3k in new tires, QTP downpipe, Cobb AP stage 2 and some others im still waiting on. On stock parts I was running 15.1 @ 89mph. After these mods Im running 15.2-15.5 @ 94mph. Im running the same 60' & 60mph faster in the 1/8th?? The more I dump in the slower it goes???? and 2) goin down the hwy in 4th or 5th gear at 3k rpm and then just slam the gas down I boost up to 16 psi then down to about 11 and back and forth till i let off. It only does it in these two gears everything else just sticks at 14-15 psi?? Am I in need of a tune?

 

you typically do not reach maximum boost until about 4th or 5th gear (you will not be boosting to 16 psi in every gear). As far as the slower times, I would try and get a tune; some cars do not take well to the Cobb base maps, but others do. In any case, if there really is a problem then your tuner will most likely be able to tell you.

 

+1 i think its the AP after i tuned my car the boost fluxuation went away

 

you should always tune your car shelf maps are ok at best.