I remember a long time ago there was ton and tons of discussion and even some heated arguments over cackle and knock. There was even a guy with the initials of KL that was having people sign a non disclosure agreement to get in on his so called fix. I ended up going with the Hutch mod with the Housted T and went with the Billet FPR and black spring. My cackle went away mostly but the knock never has. I replaced the Long Lead #8 injector with a an AD, helped a little. I've done the FRX, HPX and CVD fittings change out, still knocks. Fuel pressure stays at 68 to 70 psi always. I am done I am not going to do anymore chasing the elusive knock fix, if there is such a thing. I think the only way to get rid of the knock is change the firing order, which we all know cannot be done. The one thing that still gets to me though is why, every once in a while the motor will smooth right out and just purr no knock, no rattle just pure beautiful diesel idling away. It's a beautiful thing.