I forgot that thing was EFI.

I would think it would be even more important to insure the fuel pressure is constant with that set up.

What system are you running that operates at only 6psi(or did you mean 60psi)?

Edit: looking at the specs for the Walbro 255 pump, I’d say you’re at the point where it may just not be enough pump.
It’s rated for 630hp........ going by this:

D0747162-4C3D-4CC4-BCF1-1DBDBA787F94.png
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads