I have a 67 Pontiac 428 with a manual transmission I have had the carburetor rebuilt by a good shop but they can't seem to make the idle smooth it seems to be starving for fuel they have gone through everything but something seems to impending the flow I'm wondering if the hick up is in the tubes or if maybe a later model gasket could be blocking a passage they rebuilt another 67-8 quadrajet but it is having the same issue they have always done good work for me so I'm puzzled