i dont think 3-4 lbs at WOT is a problem.I'm losing about 3-4 pounds at WOT on an extreme file. Thinking it might be time for new fuel filter for my FASS.
During the fall of '02 Mike Halas was looking at the DI regulated return system in my truck and stated that feed was very restrictive and he was feeding both heads directly into the fuel rails with a custom made fitting that did not use the OEM feed. I have not looked closely at this but IIRC, the fuel rail is drilled in the head and then plugged at the rear. I believe he left the OEM plugs used by most aftermarket fuel systems in place and modified the heads to accept his custom feed. Of course, the heads had to come off to make this happen whereas the JnB and DI kits did not.I turned mine down from 68 to 59-60 recently and the truck smoked less and ran noticably cleaner and crisper.
This only further prompted me to do away with the flow through the head design because of the probable fuel aeration being created at the entrance to the heads being worsened by the increased pressure ahead of these two ports making the pressure drop across them worse leading to an even bigger aeration issue.