fuel pressure drop

No I don't think that. Actually I would suspect stuck open first. And plugging the outlet or pinching it off could prove that, when the revs go up.

But like the guys said before me , that style of gauge is temperature sensitive, and I have seen a few guys get fooled by them.
That's one of the reasons I have no aftermarket gauges on my car, except a tach, and I only got that, several years after the build was complete.If I don't have gauges telling me bad stuff than I don't have any worries.If I don't have any worries than I can be having fun. I like having fun....... Most of the time I don't even watch the tach. I mean it doesn't tell me anything I don't already know.....It's just there to impress a passenger, who has never seen a Mopar go into the 7s......