It depends on the model - not all 1992s had the issue as this year was when MB was phasing in changes across numerous model lines, switching from M103 to M104 engines in the w124 sedans and wagons, and so forth. But very definitely 1992 model year V-8 cars using LH injection had the harness issues. I don't believe that KE-Jetronic injection V-8 or inline-6 based cars (which your 1992 500SL would have been, if I remember correctly) had the harness problems. I had a fairly late-production 1992 300TE wagon (M103, KE-Jet) and it didn't have the problem.