Have a HP950 on this new motor. Good carb Ive had for years. Dyno session went great. so now in the car I have this annoying miss right around 1800 to 2000, only at cruising speed(very light throttle). I think its having trouble between the idle and main circuit. Give it a wee bit more throttle and its gone. It did not exhibit this last year on a different engine. Engine makes about 10 inches vac, at 1200 RPM idle, so I have 5.5 power valves in primary and secondary. Tried upping the idle air bleeds from 74 to 78, with no perceptible change. Have not changed main circuit air bleeds. Thought maybe a power valve change? When the miss is there, my AFR goes to an11:1'ish rich condition. I'm sure as hell not a carb expert and could use a suggestion or two. It's driving me nuts. With a 9 pound flywheel and 4 speed, these kind of things can be amplified and be REALLY irritating.