I've been on the autobahn (as a passenger) many times and have seen speeds up to 245K/hr.
People don't travel at that speed on those (designed for high speed) roads unless there is good weather, low traffic, and most importantly, they know their cars and how they'll perform. They don't take a car with questionable tire inflation, questionable shocks, etc. and get in a left lane.
IMHO what you did was very dangerous.

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1985 300D cali 190K

http://mercedes.thatchermathias.com/mw300d.jpg