car runs rough. sputters and back fires unless I let it warm up for three minute

Not sure how it is on your Camaro, but most cars have a 'cold start' function which adds extra fuel while the vehicle warms up. There may be a cold start valve or a water temperature sensor involved in this process. If this sensor or any component involved in this process is bad, it can cause problems when the vehicle is cold until it warms up. A good shop should be able to diagnose and find this problem fairly quickly.