Hi, i have noticed a exaust leak from the turbo.
it looks like its coming from the entry of the actuatorarm. I have thought replacing the whole turbo but im wondering if there is a cheaper alternative, i had no luck finding partnumber nor someone else having the same problem.

 

I also have an OM642 and was recently trying to track down a potential exhaust leak. I found a similar leak on my turbo actuator but ultimately diagnosed my smell as oil leaking from the vacuum pump and burning on the exhaust manifold. I can't say for certain, but I'm wondering if a small leak from the actuator might be okay for a high mileage car. I had no visible soot in the area which further made me comfortable with leaving it for now. Here is a pic I took when troubleshooting mine.

 

i have thought of leaving it until it starting squeealing when i reved the engine. Everyone can clearly hear that there is a leak and also i only have about 100hp because im loosing boostpressure so i need no fix somehow.

 

Mine makes no noise and no loss of power, so yours must be way worse. You may want to check other common leak points... the flex pipe behind the turbo being another that is in the same general area. Are you getting any codes? I am surprised a leak through the actuator could be that impactful to performance.