[George Mirza]

Phil,
If it is a carb problem, it's most likely the secondary side. Check that the air valve is free and the stops set properly. Also look at the secondary vacuum pull off. Make sure the vacuum line is hooked to the proper port. There's two, make sure it's on the one furthest away from the pull off, it should have vacuum at idle. If this is switched the air valve will only open partially making the carb go rich like Jim said.
Good luck,
Let us know how you make out.

George