The time my fuel pump went weak I couldn't get boost past 5 psi without knock. On the fuel pressure gauge it would go up to 46-47 psi and then would suddenly drop off if I tried to push it any harder. Other than that typical driving around not getting in the boost was fine. The pump even showed a steady 42 psi at idle w/o a vacuum on it. (i.e. vac line removed) Replaced the pump (it turned out to be one of the notoriously defective F2000169 pumps) with a newer Racetronix Walbro pump but still had issues with fuel pressure dropping off, except now at 52-53 psi instead of 46-47 psi. Changed out the fuel filter and all was good again.