Fuel pressure issues..... Confused....

Want some input from you guys... Okay so her is the issue.... Im running a BBK 190lph pump feeding into a BBK adjustable regulator. Fuel pressure with engine running and vacuum supply OFF of the regulator is 45 psi. Attach vacuum hose and goes down to 40 psi... when I open the throttle fuel pressure drops to 30-35 then comes back up.... Called BBK and the dude said it is suppose to do that because of the fuel the injectors are using.. Every Mustang and 5.0 I ever remember working on in the past several years I remember the pressure increasing 5-10 psi under acceleration (higher engine RPM when vacuum goes away) to compensate for the extra fuel the injectors are using... This is my thought... PURPOSE:
The fuel pressure regulator controls fuel pressure supplied to the injectors. The regulator also traps fuel during engine shutdown, thus eliminating the possibility of vapor formation in the fuel line, and provides instant restarts and initial idle speed...OPERATION:::
Balancing one side of the diaphragm with manifold vacuum maintains a constant fuel pressure drop across the injectors. Fuel in excess of that used by the engine is bypassed through the regulator and returns to the fuel tank.

Am I right and did I just happen to get the idiot of the day at BBK???:shrug:
 
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I agree that it should not go down when you rev the engine. As vac goes away, fuel pressure should increase. If it doesnt, I would think there was a rectriction with the flow. either clogged fuel pump strainer, clogged fuel pump inlet (not likely since its new) clogged filter, crimped line. low voltage to the pump caused by a wiring issue, relay, bad grounds or charging system fault. maybe even manufacture defective new pump.