Does it feel like the car doesn't want to go until 3000 RPM's? That's how my wife's Mustang feels, 2.73 gears suck at the drag strip (great on the highway though).
After mine got done spinning it took the rpms forever to build back up or so it seemed. Then for the the same kinda feeling as what you mentioned occured. It's frustrating and I really wanna get different gears now...really bad.
2012 v6 mustang base grabber blue auto
Performance: bbk lt headers, bbk o/r midpipe, thrush turbo mufflers, MPT 93r tune, airaid CAI, 3.73 FR gears