Is there any way to tell whether the carbed 308 is running rich or lean without an elaborate CO tester? Mine failed the California smog test months ago. It was running too rich. Too much CO. Now I've finally finished tuning it up and need to pre-test it before I take it for an actual smog test. I've already turned all eigtht carburetor mixture screws all the way in and then backed them off 3 turns (and I assume the manual means 360 degree turns). The carburetors are all balanced at about 3.75 kg/h using the SK-1 synchrometer and the idle is set at abouit 900 rpm. Timing is set about 8' or 9' before tdc. Is there a clever home method of pretesting the CO level? Like maybe holding a peeled apple or potato up to the exhaust and if it turns a certain color its rich and another color if its lean?