Have you checked the delivery valve seals (on the IP)? They tend to create nailing at idle where the rubber o rings are leaking. Its a lot cheaper fix than cleaning and calibrating the nozzles. The torque sequence is a bit odd but other than that and the fact that you need to remove the injector lines to get at them.
I would suspect that first then have the injectors pop tested if the noise persists.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!