|My apologies to Oliver, I'm getting too impatient again and so look forward to the note!
As to the Mass airflow sensor, Geoff, I'll readily admit that this is an area I know little about and suppose that it is because normally we never hear of any problems concerning it. As Oliver saw, the performance of the engine is affected from starting problems to actual running power i.e. stalling and shuddering etc. etc. Within the sensor unit there are two sensing wires that can become dirty, apparently, from small particles and thus affect the functioning of the sensor itself confusing the electrics. The two wires heat up when the engine is running and measure the actual air flow and detecting how quickly the inflowing air cools the wires. I believe they are accessible and one can take off this small unit and carefully clean up the sensitive wires from debris. It should then function properly again. I cannot say whether the unit is sealed or not, quite frankly.