320 Lph In Tank Fuel Pump And Stock Regulator? Excessive Flooding?

i doubt it.....but i could be wrong, its happened before

im pretty sure people run the ford GT pump with the stock FPR and that pump is 310lph

310lph pump here with stock FPDM and no problems

Help me out here. This is a return fuel system correct? Why hasn't the fuel pressure been measured/logged then you would know?

The post doesn't state how the 37 PSI measurement was done. Because 37 PSI at idle is too high if measured with an external gauge at idle. At idle there should be a vacuum inside the intake. The fuel pressure should be closer to 32 PSI.

Has the intake vacuum reference line been confirmed connected and leak free?

The other thing that's not correct is the fuel trim values. If the fuel trim values are correct but the spark plugs say rich, that says to me "EXHAUST" leak or the PCM closed loop processing is not working.