What is the problem? on 2002 Pontiac Grand Prix

I have a 2002 Grand Prix GT 3.8L. Just had the upper and lower intake gaskets replaced, the valve gaskets replaced, a new radiator, and a new 4th gear shaft put in my transmission as the car was not shifting from 3rd to overdrive (this works fine now). The problem I have is that when I depress the accelerator 1/4 to 1/2 the way down (seems like the same type spot each time), the car starts to jerk and the rpms go up and down during acceleration. Once I push the accelerator more to get past this oint, the car accelerates fine. This mostly happens when going up a hill and trying to maintain power going up the hill or, when accelerating slowly. When I punch it, no issues.

by in Waukesha, WI on February 06, 2013
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1 answer 2 comments
ANSWER by , February 06, 2013
do u have any eng or trans codes? if not read fuel trim with scanner to see if its fuel related or poss vac leak
COMMENT by , February 06, 2013
I agree with greg
COMMENT by , February 06, 2013
No codes are being thrown. My buddy has a scanner tho.