...$25 fpr
A walbro, without any kind of voltage booster, will put out 43.5 psi @ 13.5 volts. So at least at idle, it's doing what it should.
If I were a betting man, it's that piece of junk FRP. Get one from a reputable company that's known for fueling (Aeromotive, AEM, Deatchworks, etc)