The 6.9 installed in my bronco has taken to making a spark knock sound under a load, it doesn't matter if the engine is cold or hot it makes this sound and I am assuming I need new injectors as I have already removed the valve covers and checked the upper valvetrain for any issues as well as started the engine with the covers off to make sure all the rockers were being oiled. The engine seems to run smooth, start easily and does not make any peculiar sounds at idle it also has better oil pressure than my other 2 idi's at around 25psi hot idle and 40-50psi out on the road. The reason I think injectors is until last year this engine hadn't been warm since the Clinton administration. I will also add that the engine was rebuilt right before it was parked but I don't know if the injectors were replaced or not. Thoughts?