That is your only problem. Anything above 1000rpm under no-load is not governed by the IP. If it goes above 1K (After the AC turning off for example) the IP won't control the amount of fuel injected, and soon you're at 5Krpm before you know it. Don't ask me why, I have no clue.

If you turn it down, even to 800-950 range your problem will completely go away. On the OM617 it is very easy to do. Look on the side of the IP, there should be a point (Only one point) that the linkage hits against. There should be an adjusting screw with a flathead screwdriver slot and a locknut at the base. With the engine on, loosen the locknut and back out the screw until it's where you want it. Easy as pie.