Engine hesitates and sometimes stalls shortly after ignition
The problem first appeared months ago with little symptoms: just little hesitation after engine was started and after a short while engine was back to normal. However it has slowly gotten worse. Now after engine start, it hesitates badly and sometimes even stalls.
This happens with both hot and cold engine. It starts right up but starts hesitating badly after about 5 seconds of idle. It lasts about 15-30 seconds and then starts running normal. No smoke and drives just fine after this. Often it is so bad that the engine stalls and takes lot of cranking / giving more gas to get it running.
New fuel pickup in the tank, fuel lines, fuel filter and fuel pump (acdelco) were installed about a year ago. Car has mechanical IP which was rebuilt few years ago and marine injectors installed. I tested 7 of the 8 injectors with a cheap injector tester which showed injectors popping between 1750-1900psi with ok spray pattern in each and no leaking. I don't know how old the glow plugs are. Engine was rebuilt some years ago and eaton m112 installed.
The engine shakes a bit on idle which goes away when giving bit more gas.
I'm out of ideas what to check. Suggestions are appreciated.
-89 K1500 Z71 6.2d with Eaton M112