fuel rail pressure

[young12valve]

Info on truck, zf6 2005 lly. s475 over stage one powermax vgt. 60% injectors and twin cp3 both stock pumps. airdog raptor 150 feeding it all. So at times during idol my frp (fuel Rail Pressure) will dip down to ~4700ish and while driving normal I have no problem, but during wot it will drag frp from 22,000 down to 4,000 psi. Then at other times at idol frp will be at ~5700ish what should be normal. So my question, is it my lift pump that is not fueling consistently or some other problem. any help will be appreciated.

 

[JD4440]

id bet some other problem. Im not sure if a raptor is a flow through pump or not but it shouldnt effect idle pressure if it is.

 

[99f350]

I had similar issue, also a lot of fuel knock if I stood on the go peddle. Tune was my biggest issue