I've got a 5 . Slow!

[BurninBurt]

I've just got at 91 GT with lots of little goodies: a K&N air filter, off-road H-pipe, 2 chamber flowmaster exaust, and 3.73
gears. Also it's a stock Ford AOD automatic with a shift kit (dont know what kind). All this....but it still feels like i'm driving a brick down the road. I know my TPS (throttle position sensor) is bad, and am going to get a new on. But could that
make a big difference when I'm at WOT (wide open throttle). Also I have a friend with a 92 GT with a heavy duty Borg Warner 5-
speed. And his car is like a bullet, he has a slighly bigger cam (operates from about 2,000-5,000 RPM). I added that because I
base all my comparisons while riding with him. My engine was rebuilt only 8,000 miles ago so I know it doesnt need a tune up.
Anouther problem is that the car will not stay in second gear unless the I put the pedal to the metal, and then when I'm in
any gear , except 1st, the engine seems to raise its RPM's very slowly, by the time it gets to about 4,000 or 4,500, the needle
is just crawling! I know I have a ton of questions but anybody with any suggestions would be a big help! thanx