Setting for a pass level is one thing, setting CO so the car runs properly is another. At 3.5% the car will run pig rich and probably load the plugs at an idle. Does this car have an O2 sensor? Phil mentioned the test connector was deleted, if there is in fact an O2 sensor and frequency valve then no test connector is needed. Simply backpin at the frequency valve and read the duty cycle directly. Make sure to do this with the exhaust good and hot after a drive to make sure the O2 sensor is up to temp and swinging properly. Aldo if there is O2 control there should be a white 2 pin temp sensor on the bottom of the upper coolant neck. This will report to the jetronic control unit when to allow O2 control. Make sure this sensor is working properly. I can dig out the book of Bentley later this afternoon and verify pinout and functionality. I need to get the house picked up and go to our annual free whisky tasting
Cheers
Dan