Being a former owner of a '90 300CE, I did a fair amount of searching to improve engine temp and performance. Go to this site:
http://pages.prodigy.net/jforgione/MB_CTS.html to read about lowering engine temp which keeps the timing from being retarded so much. I was tired of the anchor my car seemed to be dragging when the engine temp approached 100C.
You can also play with a resistor (which on my 300CE was located on the drivers side wheel well) as described at the following post:
http://www.peachparts.com/shopforum/showthread.php?threadid=32224
I once read that available in Europe was a dash mounted switch that would allow you to change this resistance on the go.
I currently have a '92 500SL. This car is great but designed to run fast. The 300CE was a super commuter as performance from 60 to 90 mph was awesome. The VVT advances at 3000 rpm which is approx. 60 mph. Oregon has a new law which gives you a free ride to jail if clocked over 100 mph. I'm currenly trying to connect with a '93 300CE Sportline to replace the 500SL.