I just got done installing a brand new 4t65e-HD in my 97 GTP. Bought from Certified Transmission, who also built/reman'd it. The problem is hard to explain other than the car just feels much slower than before. 1-2 shift is slow and un-firm, and feels like it's lacking a lot of torque. Some paperwork that came with the trans said I would need a case learn, but after searching around on here, it seemed unnecessary. Also, they suggested cleaning the MAF for some reason. Any ideas would be greatly appreciated.