Pressure Regulator

pishta said
fuel height is more important than may be thought, especially for idle. On a slant is it the first thing you do after a valve adjustment. Reducing the pressure feed to a carb is not going to change AFR unless the fuel is blowing the needle off the seat. Carters like 5, Holleys like 7.
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Yes and its first thing Holley says to check and adjust when installing one of their aftermarket carbs.

and exactly. The hieght of fuel in the bowl is determined by the float position, pressure only makes a little difference if any (unless the valve can't hold it).