Engine noise diagnosis

[w123fanman]

Well I know this is a fairly common question but I have some injector knocking that I don't know the source of. 190D 2.5, nearly 320K miles.

I had my injectors cleaned with the nozzles changed and balanced by Greazzer, installed them around 2000 miles ago. I changed the delivery valve seals and washers only about 100 miles ago because I had a leak on 2 of them which I assumed could be causing the knock, unfortunately I am not sure if I torqued them down right because I have a harbor freight torque wrench and I didn't know until afterward that I should have calibrated it before using it.

I honestly don't remember how long I have had the knock or if it started after I put in the rebuilt injectors. What I do know is that injectors 4 and 5 are pinging, iirc 4 is louder than 5 (using a mechanic's stethoscope and with feeling it). When I start up the car and it is cold this is very loud, louder than my 77 240D's idle, but if I drive it out on the highway and get the engine well warmed up, the engine quiets down a lot and runs a lot smoother though though those two injectors are still a but louder than the other 3.

I don't think I have any issues with air leaks in the fuel system but lets not rule that out.
The motor mounts are shot and probably contribute to the noise but I don't think they are causing it.
My guesses include the balance of these two injectors is slightly off (also unlikely) or my injection timing or engine timing are off. I have no record of if the timing chain has been replaced but I don't have any symptoms of the chain needing replacement.

Any other ideas?