OM642 highway steady speed performance
 

2007 E320 with OM642 with 190K km. (112K miles)
No codes. The car runs fine when cold. The engine feels like it "sings" at a proper tune. I'm not sure how else to describe it but it's not struggling.
But with time (about 30min) perhaps because of heat, it feels like it choaks a bit. It just doesn't feel like its running strong. I have to come out of cruise and give it some throttle to wake it up.
fuel filter is good. Only 20K km. TB cleaned recently.
Air filters should be changed soon as I believe I'm coming up to 40K km mark. Regardless of the current mileage they should be ok though. I'm sure I don't have any turbo air leaks.
thoughts?
Thanks for input

Start with basics
-run engine smoothness test
-check the intake flappers rods for good connection and smooth operation
- install vacuum gauge on the intake to see status of air filter
-monitor dpf status
You can also use infrared thermometer to see if all cylinders are operating with the same temperature (hard access on this engine)

It looks like it was my engine air filters. Christ they were awful with only 20k km!
I had them checked at 20k km and they looked like new! Go figure.