Mechanical Problems & Technical Chat - Backfiring

well i posted before about my idling and surging issues... well now my car has backfired twice. i cleaned the injectors out and the basics, but now since it's backfired twice i'm getting more bummed out. help?!

Check all spark plug connections...may be a good time to change them...

Cat going out? Maybe o2 sensors going. Leak in the exhaust somewhere, or a bad exhaust gasket, too much fuel, etc. All are causes, and there are causes for these causes.