I think it is the timing all so it is very sensitive, I strongly recommend obtaining a proper timing tool to set it correctly. with a ferret timing tool with todays low cetane, fast burning diesel 6.5-8 degrees BTC at 2000 rpm(mine reads 12.5 at idle, and 6.5 at 2000) under light loads and if you never tow, more advance can be tolerated, however if you tow and will have long periods of full throttle, less timing is better. as the engine can thermal forward under prolonged high egt's . diesels never idle to Rich. they can be smelly if an injector is bad, (weeping) on pressure build up. hence fuel in cylinder at the wrong time, incomplete burn means smelly, smoky, exhaust, get it timed, then see how she runs, then adjust fuel rate. my .02