No high rpm engine speed increase
 

95 e300d 125k. Trusted indy called me and said there wasn't any power past 4k rpms. He said a relay that controls a secondary set of "flaps" was getting power but not working. It is true that the car is a dog and never "steps down" at speed. I guess it doesn't step down cause the broken relay can't make the engine breathe enough. Does it sound like I understand the problem he was describing to me? Any additional help is greatly appreciated.

Yes, those are the resonance flaps in the intake manifold. Sounds plausible.

Since I have never seen under the hood of an E300, what are those flaps for? Do they act like a throttle or just to lower intake noise?

They change the length of the intake runners. Longer path at low rpm = higher torque. Shorter path at higher rpm = better breathing for higher horsepower.

MB has not been sitting still. They keep improving these things. ;)

How about the butterfly valve on the intake of the 240's I've seen? They don't look like a shutoff valve since the clearance around them is too much...

Mine doesn't have one, so I can't help you there. But it has been written about here if you care enough to search for it. Maybe some sort of emissions control.

On mine it controls the vacuum the I.P. governor feels...