As soon as I let off the gas completely, the pedal will often get stuck all the way back and i'll have to give it a little force to move it, which results in bucking. Any ideas?
Get under the hood and work the throttle linkage at the throttle body by hand from the closed position. Check for stiction, binding, interference with other parts etc.
SteedaGT9150, in addition to what Noobz347 and trinity_gt mentioned I will add that sometimes there is carbon buildup at the throttle blade. This will cause the throttle to stay open. You can spray it down with some throttlebody cleaner and see if that help.
I try to lube the throttle cable at least every year. Some oil on every linkage and a little down the sleeve helps a lot. You can use WD-40 or JB-80 to free it up initially but you need to follow it up with 3-in-1 or a couple drops of motor oil, as spray oils evaporate leaving little to no lubrication themselves.
Years ago I had the same problem when I bought my PP TB and upper plenum. The throttle was sticking open about a week after the install. I used some throttle body cleaner and it was fine. I had to do it again a few weeks later...after which I never had that problem. A shop told me that this sometimes happens with new TBs.