I can measure/check my pulleys tonight, but that fuel system does sound WAY undersize. I am running the "8 psi" pulley setup on my bone stock LT1 with 1.6 rockers and good exhaust and was seeing 10 psi @ 6k rpm. And with 36 lb injectors, datamaster was showing 95%+ injector duty cycle. Based on 1/4 mile mph, I was making about 380 rwhp.
I am not sure how they came up with "18 psi" setup, but I try to think about the blower not as a pressure pump but a flow pump, which it actually is. If the engine flows better, then it won't build as much boost given the same blower speed. Look at Jeff Green's car. I think he is only running 15-16 psi, but making 1400 hp.
Also, does the setup your working on have a dual feed setup for the rails? That is a big deal IMO to keep from starving the last 2 injectors in line of the stock setup.
The stroker I had in my car, was run on "the 15 psi pulleys" made just north of 600 rwhp and was producting 12-13 psi boost. On the stock single feed setup he got fuel starvation and had to go to dual feed setup. It was also running on Delphi 50 lb injectors.