Here's the e-mail back from SuperChips:

"After doing some checking I have located a file for the 1994 Mercedes 420
4.2 liter automatic. The cost for a chip for your vehicle is $395.00 plus
shipping. We will need the computer code that is located on the computer
box. This code should start out 0280-002-***. Once we have this code we will
be able to tell you if we can do a chip or not

Thank you for your interest in Superchips http://www.superchips.com/
Nearest Dealer 1-800-898-2447