OM642 Carbon dust on underside of turbo heat shield

[87tdwagen]

Hi all,
Doing a routine check of my OM642 turbo actuator rod, I noticed a good amount of powdery carbon build up on the underside of the heat shield. I could not see any obvious traces of carbon on the turbo body exhaust side with the exception of a slight trace from where the actuator arm enters the turbo body.

I did notice a slight amount of carbon on the main exhaust pipe to turbo connection down low in that corrugated metal union between the turbo exhaust pipe and the rest of the exhaust, but most of that is not under the heat shield and the surrounding areas seem fairly clean. Felt around for leaks but did not detect any by hand.

Any ideas as to why the underside of the heat shield is covered in carbon?

For now, cleaned up the area and cover and will monitor. The actuator arm moved freely in the turbo body, wondering if that little pass thru is the source of the residue. any observations, or experience others have had is welcomed.

TIA