It looks like KE 5.2 was used in all versions 300SL-24 in 92. The next year LH came in and I wasn't sure what a non US version might have. My Bosch info says all versions are KE not LH.
Anyway, fuel control will have to be monitored. Both KE and ignition EZ-K should be monitored with a scan tool for codes and real data, but the most effective way to monitor fuel control is by monitoring the EHA current.
Basics should be verified first: compression, condition of plugs, idle speed control, base setting of airflow plate. There is actually a lot to do. An experienced tech is invaluable in this situation. Not only one that has the tools but one who has the experience to know, from sight and sound, which time consuming tests to do first.