parked governor bouncing to 2100 rpm

[slowpoke]

truck starting running a little rough at idle, now fuel mileage dropped about 1 mile pg and engine feels sluggish, noticed no longer using 3/4 throttle find im right down when i never used to be and its got no quick get up and go on just fuel without turbo. have to do etest on tue so i put truck to parked max governor speed 1800 rpm just to check held it there for about 2 seconds then it gave a double kick and ran up to 2100 rpm tried 5 times twice it held 1800 other three kicks fuel twice on its own and bumps up again.
does that give any clues as why its running rough, just hoping they are connected if not what could cause the different rpms. i have swapped out all actuators some with new and some good used ones i had but no difference. engine just seems loud and not pulling strong anymore