I've got a knock that is very loud. When I crack number 3 injector line it goes away. Close the line it comes back. None of the other injectors will stop the knock. The following is everything I've done so far. All new injectors (stock). Had them check and all r good. Pressure tested all cylinders and the all r at around 380psi +- a little. Sent off an oil sample and it came back good. No metal no water. I have this posted on another sight but thought I'd see if someone on here might have different opinions or maybe have had a similar problem. Thanks in advance

 

Have you properly adjusted the valves ever?

 

Yes. Several times. Truck runs strong. Just one loud *** knock that is driving me nuts