if your diesel smokes constant black you will melt pistons or blow a headgasket, tuning a diesel is more like adjusting everything back to factory specs more precisely as
valve clearance check and adjustment
timing belt slack check
injection pump advance check and adjustment
injector spray pattern test (noise test) - as well as breaking pressure check
compression test
diesel injection pump internal pressure check
After all is done accordingly your diesel will start on first crank (not even a full revolution of the starter), your km/lit would be perfect, lubricating oil will stay relatively clean and engine will sound quieter