[Carwhiz]

First of all, there are numerous things that could be causing this problem. Bad ecm, bad sensor, fuel problem, etc... You may begin by searching for obvious problems-checking/replacing spark plugs, wires, reading any stored ecm codes in memory, replacing any necessary sensors, although, if you take it to a pontiac dealer(I know, costs!) they can run a diagnosis on the car and find the true problem of the car. It might cost you $100, but you will have the solution. By trying to diagnose the problem yourself you may be replacing unnessesary parts that could easily add up to $100+. tHAT'S my opinion!