More power at 12 psi than 15 psi, why?

[EricF]

I drive a '93 Talon with a Turbo XS MBC, a Holly 255 LPH fuel pump, and an Aeromtive AFPR (set at about 40 psi with the vac disconnected). It has less than 80k miles. Iread on this site that my stock injectors will support 16 psi tops, so i cranked it up to about 15 psi, but the power drops off as the engine raps. My car's way faster at 12-13 psi. For a while I was convinced that my bov was leaking, but i read about about how the 1g is a great bov, so I've been thinking that the car must be pulling the timing back. It's probably important to note that I live about 6000 feet above sea level, but i've traveled to places lower than 3000 and still felt the same effect. Also its usually around -20 degrees when I drive to work right now, and the car is still faster at the lower boost setting. I don't know what conclusion to draw from all of this, hopefully someone more knowledgeable than me can help. Thanks

 

[PSI NRG]

Another reason why your car might feel slower is if you are running 15psi on a stock turbo its probably pushing it to its max and there for not really making 15psi its just heating up the air and not creating actual boost. There maybe a term for this but I cannot remember at this time. I could be completely wrong but I know I've heard it somewhere... Just my .02

 

[oldman]

so its just the little metal thing on the side of the valve cover? thats it? there's nothing inside the engine thats part of it?

I don't know how much more clear I can be than post #8.

PCV = Positive Crankcase Ventilation. It's screwed into the passinger/fiewall side of the valve cover, connected to the intake manifold via a rubber hose. PCV is a one way valve which opens when intake is under vacuum to relief pressure in the crankcase and closes when intake is under boost to prevent boost from entering the crankcase.

The pcv valve is the piece sitting on the floor next to the valve cover.