1999 Whipplecharged 502 MPI. I am used to seeing 43 psi fuel pressure at idle and 50 at WOT on my Gaffrig electrical gauge. Today I get 45-50 at idle and spikes of 70-90 psi when I open the throttle. What could be causing this????? I would really appreciate any help.

check the other thread about this called "skyhigh fuel pressure" also hook up a mechanical guage first and make sure you dont have guage, wiring, or sender problems before you get too crazy with it.

Checked the wiring to the gauge. Embarrassingly enough, it turned out to be a loose spade terminal hanging on the fuel pressure sending unit.
Thanks Hillbilly.