2003 grand am gt missing

Test are best to confirm the issue and you have to start somewhere, I would test compression on all cylinders first to confirm head gasket issues, then backtrack to test the fuel injectors (are they dirty, wire harness connection good ect). Then spark plug wires, & coil, you will need a multimeter and a repair manual for the values and trouble shooting test. I would test the cam sensor, well in-fact all sensors. Cle3an throttle body & IAC & MAP, Remove the throttle body & IAC clean with throttle body Cleaner and assorted nylon brushes & reinstall with new gaskets, while only using MAP sensor cleaner on the map and do not touch the filment just spray it clean, and new air filter & fuel filter. Make sure spark plug wires are not arching on each other or metal parts, Use dielectric grease on both ends of plug wire boots. and any other electrical connection you can get too, but first spray connections out with contact board cleaner for electronic parts. If fuel injectors are dirty you can pull them and rebuild replace the filters on tips or have the internals cleaned at a shop that has the set up too or replace them or even try fuel injection cleaner in fuel tank but be sure to install a new fuel filter before hand you do not want small particles dislodging from the filter entering the fuel lines and injectors.

Could be bad coil packs fuel regulator or fuel filter.