Checking another gauge is a great idea. Also, have you ever run it with just the mechanical pump? I know some have luck with running mech/elec combo, but if it were me, the next test would be to try it with just the mechanical pump.

I have a carter 4862 on my Challenger w 505 and approx 575-600hp, and while I have never raced it so I cant say for sure if it will support it at the 1/4 mile stripe w pedal to the metal, I've never had any signs of starvation in all my test passes on the street and highway. Stock tank, 3/8 pickup and 3/8 line and no regulator.

Imo, with today’s fuels and the fact that the mech fuel pump industry is fading........ continuing to use them is just clinging to the past.

The car already has a carter electric pump on it.
Just replace what’s on there with a 4601(probably even fits the same bracket), get rid of the mechanical and all that bypass valve stuff..... done.

I may have missed this but is your gauge liquid filled ? ...on my car the gauge was reading all over the place until I drained the fluid out of it just throwing it out there

THIS was a problem I had ran into with my street M6902 pump.

Mysteriously for about 3 seasons it ran fine...no problem and in fact I needed to use a fuel pressure regulator to get the PSI down to carb tolerable 6psi.

Then all of a sudden the pressure gauge started to show lower and lower readings...I went through a litany of things, even got a replacement pump (which did the same thing). Eventually a Moparts member (Challenger 1) suggested that I dump the filter which I had plumbed BEFORE the pump. I did, and the rest as they say his history!

Here is my old post on that topic.