MF 180 needing injectors cleaned??

I have a MF 180 that sat for about 4 years, I got it running, but it blows blue smoke like it needs rings, but not all the time. The color is exactly like a diesel that is trying to burn summer fuel in wintertime. Power seems OK, but it does weaken under a big load... Sometimes, though not much, the exhaust looks great. When it is blue, I dont get an oil smell, and I have heard after a diesel sits for this long, the injectors will need rebuilt. The previous owner did the heads before storage, and I did have to have my pump done due to the internal governers plugged up with old fuel. Tried injector cleaner for 5 or 6 tanks now....Any thought?? Thanks, Digger