2001 Pontiac Grand Prix Slips at high RPMs

Hello, the other day I was on the interstate when another vehicle had cut me off. I hit the brakes, and when it was clear on the other side of me, I floored it to get around the other vehicle that had cut me off. When accelerating, it seemed like it didn't want to pick up very much speed, and was not shifting properly. At the same time, my Service Engine Soon light came on. After slowing down, the light came off.
Now, every time I try to accelerate it does the same thing, and I can hear some noises from underneath. When I accelerate slowly it shifts fine, but I can tell that it is still a little sluggish.
I just had the transmission rebuilt a year and a half ago. Is it that? Or could it be the torque conververter? Or something else?

Please help me,
Jeremy