[vref120]

Had this problem with mine also. Ran fine above 3 grand but idled or flooded the car out below 3. I have a Quickfuel 780 CFM. My sight glass would be at half for both Primary and secondary but after driving the car, the primary would overflow.
My problem was a piece if trash in the needle and seat. Not sure where it came from but got thrown into the carb. Removed said obstruction and runs fine.
However, I did take it to a good carb guy and had him go over it and tune it out. Runs like a champ.

Said trash in needle and seat. Everything else was clean.