umm, not sure on a whole lot on trans, but the PCM controls the trans, i do believe you would need a tune for the GTP trans, do some searching, sure someones ran into this. you could just do a out of the box tune from Intense but the shifts are controlled by two solonoids, a 1-2 and a 3-4 solonoid, and they shift when told to basically.
edit- Trannyman95 is your guy on trans problems, this is Dave from Triple Edge Performance, although i sent him a PM about a week ago about a trans problem and have never heard back, so you can try your luck
