I have an 06 GT auto with a JLT CAI and 91 octane tune from Brenspeed. The car runs great and normally responds well at acceleration. However, if I have been driving at highway speeds for a couple of hours and then stop to pay a toll (the car isn't turned off) it will hesitate and feel like it is about to stall completely when I try to accelerate at a normal rate. One time it also backfired before taking off. Any ideas? There has been no CEL.