I'm getting sick and tired of this problem, fellas.

I had EGR Not Ready status more than 1000 miles ago. Since then I replaced EGR Valve.
Just for the heck of it, I replaced the battery.
Also, a Mercedes specialized auto-shop has replaced spark-plugs and gaskets (as a part of a maintenance, since they couldn't find anything else wrong), they reset the computer and since then I drove about 600 miles.

And now we're back to the original problem that was never fixed - the EGR Data Not Ready.
There was never any error codes neither the check engine light was ever on.

I searched this entire forum as well as the Internet. I asked dozens of mechanics who specializes in Mercedes engines. I can't believe no one can give me a valid advice.

Please help. What else could be wrong with my car?