Hi everyone I have an 88 IROC 5.7 and if I set the FP at 46 with vacuum off, it will go down to 38 with the vacuum connected. With the engine at WOT, the fp goes up put only to about 44 or so. Why would the fp not go back up to 46? Does that mean I have a vacuum leak somewhere? Thanks for any help.

 

sounds like it could be weak pressure from the pump at WOT. the pump is asked for a lot less fuel at 46PSI during idle than it is 46PSI at WOT. Seems that the pump is fine though. maybe the fuel filter is not allowing enough fuel through at WOT to keep 46PSI.

When was the lst time you changed the fuel filter?

just my $0.02