Well I thought I would give a quick update.

I was able to get 2 good EZL's for my 420. I finally had some time last week and dropped one in. Took it for a quick spin, and everything is back to normal.. Actually better then normal. To me since ive owned the car, it always felt a bit sluggish when accelerating, and there was a slight noticeable power boost when you let off the throttle. Which had led me to believe something was up with the fuel delivery or ignition timing. But the timing always checked good at idle. (its impossible to check timing under load unless you have access to a dyno)

Well with the new/used ezl, the car now has even power delivery throughout the power band, and has some surprising punch when you stomp on it, and it kicks down.... especially above 3800rpm. Im impressed with an engine that has over 255,000+miles. I would say the car has easily picked up another 20-30hp now that the ezl feels like it is properly controlling the timing in relation to manifold vacuum.

I also finally found the timing resistor (been looking for a few years), and the timing does advance when removed.. But ill leave it in for now, until I have some time to fiddle with it.

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Just my MB's:
1990 420sel - Winter DD - 410,000km
1990 560sel - absolutely showroom mint - 360,000km!