I'd have to agree with F.J. Renntech is an independent tuner. MB should not be held responsible for some performance modified (mechanically and electronically) CLK60, CLK50. The only one to blame here is Renntech.
BTW, wire harness problems are usually associated with early 104 and some 119 engines. Even in these cases it takes many years of heat and fatigue for them to deteriorate.