Pontiac Repair: Transmission, grand prix gtp, pontiac grand prix gtp

Question
Sorry I recently submitted the following question and neglected to tell you that the car is a 2002 Pontiac Grand Prix GTP 3800 supercharged!

"Hi,
I have a 2002 Grand Prix GTP 3800 motor Supercharged.  Recently replaced the head gaskets and intake gaskets due to leaking.  We have everything back together and for some reason the transmission seems irratic.  If I accelerate slowly the shifting is normal, however if I give it a little bit of gas from a stop it doesn't want to shift until about 5000 - 6000 RPM's.  Do you have any suggestions as to what this may be?"
The service engine soon light is on, but when we had that checked they told us it was the TPS sensor, which we had replaced prior to getting it checked out.

Answer
Hi Frank:

well if there is any service engine soon lamp on that has to addressed first and foremost. if there is a TP sensor issue here then that is a big input to the engine computer to base trans shift points. If that is still acting up then it will make the trans shift hard and or late. if a NON O.E.M. part was not put on this get an O.E.M. sensor. Any other codes set in the car?