Check the injectors for good spray pattern and pop pressure.

I had similar issue in my 603 with a pissing injector in the mix. Once up to temp, it's amazing how the engine masked the injector sending a straight stream of diesel into prechamber, rather than a mist. But takes good heat in the combustion chamber to get there.

New nozzles, all set right, and stumble went away.

__________________
Cheers!
Scott McPhee

1987 300D