Ryan, I'm sorry but I will have to back away from your question. I understand what you are asking but I don't have a 300E or a 560SL, and my 500SEL doesn't have Lambda control (it's a EURO engine in a US car). The only thing I can suggest is to adjust the lambda to 50% +/- 10%. At 50% the meter can be hooked either way and you will still get 50%.

Paul

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84 500 SEL (307,xxx miles)