My '95 G with the 3.2 M104 has a distinct on/off personality. Below 3500 rpm it feels soft, at exactly 3500 rpm it really takes off. It runs pretty high rpm on the highway. I have noticed that if the cruise is set just below 3500 it has trouble keeping speed, at 3500 or just above it has no problem. Is there some variable valve timing I am not aware of? How about a variable intake flap or something? Any possibilities? The transition is pronounced enough to convince me something is wrong.

My dad's 260E has almost similar problems which I think is due to the 1st gear ratio. I've checked the fuel supply, valves, relay, and plugs - which are all in good order.

IMHO - he's better off with a newer model, though he thinks his MB is one fine example of a beautiful car. And this is coming from the same man who says my 300SE is a clumsy monster. :D

The M104 3.2 has a variable intake valve mechanism that is controlled by a solenoid. This diagnosis may require a scan for fault codes. I am not really familiar with the mechanism, but I have heard that when it acts up you can have funny behavior from the engine. When you say pretty high RPM on the highway, what RPM at what MPH. You may be experiencing a lack of high gear from the tranny..

The one thing to check on this is the variable intake flap. I have seen a few break off and cause a similar situation...You can take out the 4 bolts on the center of the intake and pull it right out to inspect.