Carb problem?

I have a 85 Silverado 2-wheel drive w/ a four barrel quadrajet - has experienced starting problems.  Engine starts but races at high rpm.  Replaced electronic choke control and this helped the racing problem a bit.  Replaced cam in butterfly, installed new carb kit.  Engine still runs very ragged and at low rpms, it backfires terribly.  Any ideas about what my next step should be?

Check your vacum lines,  you should have some on the carb, if they are leaking that would make it run funny.  You may want to check your timimng too.  That is probably not the cause but it may help.