Fuel pressure dropping

[Shitbox]

I have just recently converted my AE71 from 4AC to 4AG with twin 45 Webers.
the problem im having is that after a bit of driving the fuel pressure drops from normal rate 4psi down to 1 or 2psi, and when revving it drops to zero. The car seems to drive fine except at low revs feels a tiny bit sluggish but that may be due to needing a slight tune.
also is the car alright to drive even with this problem?

any clues or advice would be much appreciated

Thanks Ray.

[Sam-Q]

dead fuel pump