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School me on what IFR's are? ,and why should I wire them down? In your earlier post, you mentioned PVCR's also? Power Valve Circuit something? Still learning these acronyms. Thanks, Jay

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IFR can mean either the idle fuel feed or the intermediate fuel feed, they are part of the main body and to change them you need to drill and tap and use a blank brass set screw and drill it smaller than the stock passage was to lean them out, make them bigger to enrichen them, confused yet PVRC means the power valve restiction channels in the metering blocks behind the power valves, same process on them to change them. Holley has normally made the idle fuel feed, transition fuel feed and PVRC larger than needed to run clean and lean like most Mopars like it The transition slot is the rectangular slot in the throttle body that is centered where the throttle blades ride in the primarys, the four corner idle circuit carbs. have them on all four corners. Not all Holley carbs. have a intermediate circuit in them, some of the bigger race carbs do IHTHs BTW, if you look on the front of the choke tower you will see some numbers stamped into it like List 4779 or List 4779-4 or some other number after the dash if it is not one of the original 4779 before Holley started making modifications to the original design Let us know your carb and dash number