Make sure you have no air leaks in boost nipple fittings or fuel line. Use can put a small drop of blue locktite on nipples and use tie-wraps on the fuel to nipple fittings. I have used them and really engine runs as well boost sealed. Main reason for this is that engine will go very lean if the fittings start to come out or fuel tubing comes off. That's really not much fuel especially as it was idling. My guess is that the lowend needle is set to lean for a race engine.