03 Cavalier Theft System/Service lights and it now floods.

Hi everyone. I am having some weird problems with my 2003 Chevy Cavalier. A while back I noticed that when i let go of the gas pedel the AC would almost shut off and the lights would dim. They would all recover. We figured it was a bad alternator and we replaced it. During the end of the alternators life, two dashboard lights came on at the same time. "Theft System" and Service lights come on at periodic times. I was told it would need a tune up, so we changed spark plugs, oil, antifreeze and even air filter. For some reason now it refuses to start sometimes. It can be sitting in the driveway all night and first start it seems like its flooded. I have to wait a few minutes and it starts right up.

Then when I am driving somewhere like the store, it shuts off fine, I come back to the car and try to start it and again its flooded. I put the hood up wait up to ten minutes and it starts right up. Again still once and a while the service light will come on. Other times the service light stays off during the whole trip.

I can't find any rhyme or reason to why the service light comes on on occassion or why it just decides to flood for a few minutes. Very odd

Any ideas??