I've heard nothing but bad things about the Ultra HP carbs. My friend bought a brand new 950 Ultra HP and had nothing but issues with it and Holley was no help. Turns out the front metering block was machined incorrectly and basically recirculated the fuel back into the bowl when you hit the throttle. Spoke to a local carb shop about it and he has had many complaints about these carbs. Hopefully you don't have a bad one.