Bucking Problem

[blackbeltclub99]

Just got my car finished now it bucks like crazy. It will do it pretty much at random, but mainly anytime you are getting off the gas. If you are on the gas it will not do it so take offs are not bad, but as soon as you let off it will start ALMOST all the time. Sometimes it is fine and does not do it. I had it tested for a boost leak and they said their was not one, but thought it may be a TPS problem. if it is the throttle position sensor how do I fix it?

I have a 98 blacktop in a 89 coupe it is almost all stock except for 3"dp, 3" test pipe, 3"catback, 255 walbro, and an intake.

any help would be great...