If things are clean (try fuel line cleaner/gas treatment? Make shure to check for vacume leaks!
Do this buy running the motor----use a can of carb cleaner----spray around intake and carb base,,vacume hoses etc...If you have a tach hook it up..if not,,listen for the RPMs to go up...
if they do you have a leak! pinpoint the problem
usually a simple fix...If you cant find a leak Check the fuel pump pressure,,,easy..get a vacume/fuel pump gage--cheep---pull the gas line
coming into the carb plug the gage hose on the end
of the tubeing then turn the motor over and note the reading--write it down-- then call the parts guy and tell him what you read--he'll look it up in the book for you,,if its a low reading your pontiac won't idel worth a damn. Now that you have the gas line out of carb Change the fuel filter inside---I bet it will help-- e-mail me if you like firstname.lastname@example.org