Well a weak pump will run poorly untill you adjust the pressure to get it up to stock. but when the pump gets a surge of energy then it will raise the pressure higher then whatvyou set it to.

If the pump is running at half effieciancy and the regulator is set to create 45psi...then when it gets a sudden surge. It will spike the fuel pressure.

11.45@125,
stock bottom end 6bolt 2g head.
272 hks cams.
Holset hx35
Backyard biult!!