new module installed, still not starting, need help

2003 alero, this year i installed a new battery and alternator. just had oil change and fuel filter changed last week. car has stalled mulitple times since then. does not appear to be a problem with fuel pump. had new module installed yesterday. after paid for installation would not start. so i left it at the mechanics, when i called there this morning, they informed me that it started up just fine. can someone please help me i am ready to shoot my car.