I know someone who has just done an MOT on a classic vehicle. The gass analysis seemed to indicate the engine was running marginally too lean (too much O2). This could also be caused by incomplete combustion.

As it was only marginal the tester kindly stuck the tube up the exhaust of another car whilst re-running the test innocent

Naturally I have no idea where this all took place. It is probably just a story and I can't now remember who told it to me.

Peter

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