Fuel pressure with boost pump on and rpm's low in the pattern result in a high pressure. Around 8psi. Is that ok ? If so, for how long? If I turn the boost pump off the pressure drops to about 5 psi. Otherwise engine parameters where all good. (0-320)
The fuel pressure difference is simply that the boost pump puts out a higher pressure than the mechanical. The float/needle valve in the fuel bowl is modulating how much fuel enters the carb. Since the engine runs fine with the boost pump on it is all working correctly. The boost pump for a fuel injected engine puts out closer to 40 PSI and might overcome the float/needle valve. My RV4 boost pump pressure is higher than the mechanical fuel pump as well.