My cousin has a 92 500E and I asked her about this. She has not noticed any power difference at temp except for the draw of the AC compressor. And before jumping to conclusions (she being a she) she does drive the car very hard on occasion.

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif