502 mpi Fuel Pressure- need help
 

2000 model 502 mpi's: (Naturally aspirated) I rebuilt the top ends last yr. to make approx. 500 h.p. The guy that reprogrammed the ECU's suggested I buy the kits from CP Performance to make the fuel pressure reg's adjustable for fine tuning. The pressure always seemed squirrley- every time I checked them they'd be different and adjusting them was a nightmare due to the location of the reg. so I just installed Aeromotive regulators plumed into the same place as the old regulators but mounted where I can easily get to them. One motor set up easy as pie and is running around 39-40 lbs. as a starting point. The port motor however seems as erratic as ever- I set it to around 40 lbs. and the next time I put the gauge back on it was around 30 lbs. When I turn the adjusting stud it take a while to react- sometimes a minute or so, unlike the Stbd. eng. which reacts immediately. The pump is only a couple of yrs. old and has never failed to work or given any signs of failing so I'm skeptical that it's the problem. The system holds pressure normally after shut-down and takes several hrs. to bleed off any pressure. Anyone have any idea what else could be causing the pressure to be erratic??

if its erratic low, then its almost certainly a pump or pickup issue. if its erratic high than it could easily be a partially blocked or occluded return line issue ... especially if the return is done as stock back to the filter housing.