I have a 4150 that was built to the specs of my engine, but it just doesn't seem right. It hesitates off idle when I take off, and blubbers at slower cruising speeds. From 2500rpm and up the thing works great. I can go to a car show and after a couple hours, start it up and I have to keep feathering and pumping the throttle to keep it running. It smells rich but acts lean. A few of the local guys have this same carb and they can start their engines and not have to touch the pedal. I know this is kinda vague but maybe someone else has experienced this problem before or knows something I can try.