I recently bought an 89 300se. The car ran fine and idled fine most of the time. However, it did have 2 instances of start/die 4 or 5 times in a row over the course of a week. I pulled out a spark plug and discovered it had Bosch platinum infusion plugs installed. I changed them for Champion copper cores which as I understand are much better for this vintage of M103 engine.
So . . . I have this set of Platinums that look like they weren't in very long. I'm not going to use them and I don't want to sell them. If you can use them they are free for the asking. The Scotsman in me hates to put them in the trash.