why does my car die during idle? on 1990 Chevrolet Cavalier

car dies during idle, have changed spark plugs, iac valve, icm, fuel injectors, clean fuel filter, new vacuum hoses. car will run as long as i give it gas but dies at idle speed, and sometimes backfires through cylinders. sometimes blows blue smoke through tailpipe.

Asked by for the 1990 Chevrolet Cavalier