PeachParts Mercedes-Benz Forum - It's different after the service??

I have my '92 400SE serviced just couple weeks ago, and since then, I rarely drive the car. Anyways, as I drove the car today, I realized the car runs a little different. Usually, when I started the car in the morning for the first time, the engine will go up to about 950rpm for about 2-5 sec, then settle down to normal idle(about 500rpm), but today, when I started the car, the engine would stay right at 500rpm!?? Is there anything wrong with the engine management?? Or it's normal for other V8(M119)owners, too???

Also, I drove my friend's '92 400E, the tranny on his car feels differ from mine, too. When the car is in motion, and let go of the gas pedal, the engine speed will drop to about 1000rpm(as if there is a clutch that disengaged engine and tranny), no matter what gear you are in or what speed you are going. But in my car, the RPM won't drop, but stay at the same RPM. So, which of the 2 cars is faulty?? His or my??