Hi
What you have done has unfortunately become a substitute for a working barometric compensator these days. Endorsed and used as well, by the leading injection pump rebuilders that I have spoken to. As many may know the compensator is no longer supplied by MB nor Bosch (maybe lobying will help). All the compensator does is adjust the whole rpm range of the pump for rare changes in atmospheric pressure (i.e. altitude as well) and as you've discovered, screwing it in or out a bit has drastic effects on the mixture.
Being a bit of a stickler for originality and look, I have not been satisfied with the standard option from the injection pump people that you can't re-plate these compensators. The problem is, if the parts are not already internally damaged or worn out, there is a good chance that the plating process will throw the calibration of the pin that protrudes from it off. The only cure is to correct for this error by (usually) adding shims or by cutting the pin.
I have found that the warm running device, which acts on exactly the same internal pump lever, with the same big effect on the mixture, is often a likely culprit with unreliable fuel mixture issues as well. The slides can get stuck. If you clean them, and they work freely they can work for a while/ or not. If you carefully remove any scarring from the aluminum piston inside the (likewise aluminum) housing/"stack"/WRD, they may work well again, but I've also seen units that appeared to work well and shut of the supplemental air as expected, but that have become loose enough that they draw a bit of residual air that throws off the mixture.
This is one device that might fall into the category "If it ain't broke, don't fix it", since disassembly and cleaning might cause damage, but unfortunately you don't have a choice when you want your car to look and function like new.
Regards,
Tom Colitt
