Hello! I have an 87 300d with the 603. I have a noise coming from the engine under load. I thought it was a lifter but not sure. I just did all 6 injector nozzles. If i touch the number 1 & 3 metal injector lines I can feel a thumping / rhythmic knocking. It did this before I changed the injectors too. You can feel it a little in all of the lines but #1 is a little worse & # 3 is extremely pronounced. No noise at idle. Id say the noise starts at around 1500-2000 rpms.

Could this be a lifter or the injection pump? Any help is appreciated. Thanks!