Sideswipe

So i have a odball problem that doesn't seem to go away. My local tuner can't seem to figure this out either and it's been a problem for 3 months now. Every now and then i put the car into Drive and it seems to slam or jolt into first gear. We checked tranny fluid and filled it up just in case. The other thing is that there is a code for TPS, we got a new one and the code still appears. My car is a A4 with a TR 224 Cam recently installed. Anyone have any ideas?