try this on 86 560 sl wont pass smog due to timing it is at 22 btdc factory spec is 12btdc. the idle is at 900 which is why the timing is so advanced. now have resealed intake manifold repaired all vacuum leaks and replaced all vacuum lines and elbows. have replaced air slide valve and idle speed control unit. test air flow meter good tested full load idle contact switch its good coolant temp sensor is good timming set correctly. after all these repairs when you set lambda at 45-50 the idle is still at 900 you adjust lambda to the lean side and the idle is lowered to 650 and the timing is corrected to 12 btdc. then then the lambda begins to rise to 90 and the idle again starts to rise manking to timing advance to 22 again. when the cis control unit is removed from the car the idle goes to 650 and the timimg goes to 12 btdc. i am going to install an 02 on monday any other suggestions