I'm working on getting a Lonnie's Dual pumper setup to replace my stock pump, but my fuel pressure gauge caught my eye on the way to work today.
When I'm cruising and going up small hills, my fuel pressure will hold as high as 48psi. Is it suppose to do that? I thought it was suppose to hold 43.5 psi... It only does this when I'm not seeing boost.

 

Are you running the stock fuel pressure regulator? Does it still have the vacuum line connected? What is the fuel pressure with the vacuum line removed?

 

Depending on the type of regulator & the way it was adjusted, you can see more pressure than stock at idle. But normal driving pressure should not increase, unless you are running both pumps continuously & overloading the small stock type regulator. Stock regulators do not have sufficient capacity for large fuel pumps & typically pick up approx 2# at idle. This is typical on LT1 & LS1 cars.

Also many supercharged cars can see positive boost at medium throttle, increasing the pressure. This can increase the pressure slightly, but most boost gauges are not highly responsive during the first 1-2# boost to notice it.

Give me a call. I'll be glad to help you out. I'm sure it is nothing major.