You know... I've fought with HIF6s for some time on my '67 220's B20E before giving up and going to a pair of HS6s (I'll go with D-jet before I fight those things again). After motor replacement, my timing was seriously wrong, I cranked and cranked and pumped a lot of fuel into those carbs and the leaked out on the side vents. Funny, because I wanted HIFs because of the temperature compensation and specifically the fuel overflow feature.

So your fuel should be flowing over and into the main carb chamber. *or* it should be leaking out a pair of vale thingies on the side of the carbs. Those are designed to be hooked up to a fuel return system. I myself once asked if it was possible to drill out the other side of the the rear carb and route that back to the tank as an FI system does...

Anyway, I'm rambling here.
The best question about your rebuilds are the needles and the jets. What is the letter-code on the needles - BAL, BBB, BCJ?? What color is the jet? Red, Black, something else?

Any of those needles work. BAL is a leaner (emissions) version of BBB, and I know nothing about BCJ except that it appears on the Haynes SU manual. in my HIF experiences, the rebuild kits have included red and/or black jets. I've worked with the "official" SU-23 and SU23R kits...

The jets are color-coded to the model, and the B20s take a variety of needles. Rhys will know which is which for sure... So a matched needle and jet set may not be your real issue.