Hi guys and thanks for the input

The car does have a OE CAT, we took off the clamp and looked inside of it to verify, we can see a mesh type honeycomb which is not blocked.

Looks like the OM 648 motor E320 in NA have one CAT right after the turbo and then 2 rear mufflers.

I do not believe the exhaust is the culprit.

Mass Airflow Sensor under load 900MG of flow.
Boost pressure 2300MBAR
Rail Pressure 1600 BAR
Removed clamp on downpipe and test drove, no changes

New fuel filter, new air intake temp sensor new pressure boost sensor, new MAF
New thermostat runs at proper eng temp.

I cleaned intake and checked intake port flaps and all ok. Also did the test on them on the car.

I have comparison to same car that has a much better perf.

0 - 60 is around 9 sec.

Like I said car runs well with no stored codes.

I do not hear any boost leaks, do not see any issues with that.

EGR is clean and was clean when I first removed it.

Seems like I have reached all the items I can check...