Hello, Scotty. does it stand to reason, that when some cleaning additive like 'injector cleaner' or 'catalytic converter cleaner' is added to fuel (petrol/gasoline) the O2 sensors, and therefore the ECM, will not read pure fuel combustion, and will indicate a condition of 'lean' burn?  Under this condition, the ECM adding more fuel will not correct the lean burn effect, and the engine will continue to run lean.  Consequently, would it be right to say that A/F and lean/rich diagnostics will not provide correct results when some sort of additive is added to the fuel (in any proportion.)  Mechanically speaking, the way the pre and post catalytic converter O2 sensors are set up (specific to engine design), and the ECM response, true A/F ratio and lean/rich burn results are only accurate when pure petrol/gasoline per manufacturer grade quality and number is used.  Could you provide your expert experience/knowledge on this subject.  Thank you. Peter.