rocky321

08 GT automatic. 90,000 miles. When accelerating on the highway as to pass someone, but not kicking it down, there is a bog down. However if you ease off the pedal, it accelerates normal. TPS?

Daniel98GT

Do you have any mods?

rocky321

CAI and 93 octane tune. That's it.

Nuke

It's either related to the TSB for the fuel pump (after cruising at a steady speed for a certain period of time, air bubbles form in the fuel pump where going near WOT or WOT forces these bubbles thru the fuel system causing hesitation) or your TCS is causing you to cut fuel/spark. I had the latter issue and make it a habit to turn off TCS unless the roads are wet.

SpartaPerformance

I would agree with NUKE but I believe that TSB is for 05-06 models, this poster has an 08 however 90k miles it may still be a fuel pump.

Nuke

Quite true and I'd be surprised if it WAS the same issue as the TSB calls out but we've seen other TSB's for specific years which were also applicable to the later year models.

NavyStanger

I have an 05 and after mods, the TCS will definitely cut my fuel during a highway downshift.

May be related to getting some wider rubber out back too. Either way, I cut the TCS off on the interstate.