This engine has had a VERY unusual problem! Haven't seen any burnt valves on that new of an engine!
You want to have the compression tested, ALSO a cylinder leak-down test at the same time. That should show whether or not the engine has been repaired properly.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)