Injector Knock before turbo spool?

[Cory]

What makes the injectors knock from idle til about 5 psi boost? With just the Edge Juice?

 

[JStieger]

My truck did this a couple of years ago and I found that my injector tips were carboned up so bad such that off idle they were just dribbling. As the boost (load) came up and the ECM started fueling, the rail pressure would accordingly increase and then overcome the carbon blocking the spray holes on the end of the injector. Just before the boost came up my truck knocked like crazy and it blew white smoke because of the late injection timing from the carboned up injector.