I think I will finally go for it: However, I have some doubts after reading the "Bosch KE3-Jetronic Mixture Adjustment" document:

Do all of the cars have the tamperproof tower/ball? If I remover the filter cover, can I check that?

When testing the duty-cycle measurement before turning on the engine, it says that you must deflect the air flow sensor plate to test the idle contact: does that mean that I should remove the filter cover and press the plate down a few mm or what?

Thanks for your help.