Fuel pump or filter possibly

try some STP gas treatment with some Shell gas you may have gotten some bad gas in your car with to much water in it make sure you pump in a half tank of gas then put the STP gas treatment in and top it off and drive it on the highway or where you can drive around 55-MPH have someone to follow you just in case you have problem i also would like to give you this information they sells only GM-parts its Schram auto & truck parts 1-800-292-1032 and they website is www.schramauto.com it would not hurt to give these guys a call since most of them work for GM best of luck Michigan Man. try some STP gas treatment with some Shell gas you may have gotten some bad gas in your car with to much water in it make sure you pump in a half tank of gas then put the STP gas treatment in and top it off and drive it on the highway or where you can drive around 55-MPH have someone to follow you just in case you have problem i also would like to give you this information they sells only GM-parts its Schram auto & truck parts 1-800-292-1032 and they website is www.schramauto.com it would not hurt to give these guys a call since most of them work for GM best of luck Michigan Man.

check all the vacuum lines and check the EGR valve you may also have a leak at the gasket surfaces of the intake manifold or a bad throttle body gasket or a fault in the fuel injection system if you can get your hands on a Haynes auto repair manual for your car they are a great i have one for every car i own stop by your local library and checkout one and you see what i am saying stay in touch Michigan Man check all the vacuum lines and check the EGR valve you may also have a leak at the gasket surfaces of the intake manifold or a bad throttle body gasket or a fault in the fuel injection system if you can get your hands on a Haynes auto repair manual for your car they are a great i have one for every car i own stop by your local library and checkout one and you see what i am saying stay in touch Michigan Man