I drilled and tapped them for adjustable IFRs. I believe they were like .025" stock, which is too small for a hotrod motor. With IFRs so small, you end up opening the IM screws way too far, which makes the idle AFR way too fat to achieve an acceptable transition AFR. I think I ended up with .031"-ish.
Higher float setting, fuel pressure, larger squirter and cam, etc may also help a tad, but are sort of bandaids for fixing a Holley Street Avenger bog IMO. Open up those IFRs.