First off, are you sure the vacuum line for the fuel pressure regulator is connected to a port on the intake manifold?
I would check your fuel pressure as this will save you alot of trial and error. You should see about 36psi at 0 manifold pressure. Then you should see 1 psi increase per psi of boost.
Monitoring your fuel pressure while running can be a pain, but you can get creative with a temporary solution..
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Assuming you do not see expected fuel pressure at boost, as you already figured i would check your voltage at the fuel pump at full load.