Ouch, that hurts. Agree with Fred's view; the dealer owes your friend better than that. It could be EHA (it controls fuel adaptation ratios) or possibly even throttle valve switch (controls wide open/full load throttle response). The point is, a capable tech would start with standard, well-known diagnostic tests to see what's causing the symptoms.

For the future, you have two highly-regarded independents in your area that would surely do a more competent diagnostic job than what your friend got at the dealership. Steve Brotherton's Continental Motors in Gainesville and Pierre Hedary's shop in Titusville are well regarded by knowledgeable Benz owners. One or both may even give a courtesy discount to MBCA members. Once your friend gets the dealership to provide some gratis repairs out of this, bid the dealership adieu.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't