I'm experiencing something similar although i've never noted the rpm's when it happens. I've had mine in for the intake manifold replacement twice. They've done some kind of wiring repair, twice. And on the last visit, they said there was no signal between the pedal and the TB so they performed a pin test and ended up replacing the ECM. They had the car for 3 days and the hiccup is still present. My car is stock, no chip or intake although they did try blaming the sprint booster even after it was removed.