The "emissions high" light (toxic light) came on the other day and was accompanied by an engine misfire at tick over. I checked the voltage on the lambda sensor and that appeared to be working okay. Next I tried pulling a plug
one at a time, but the engine refused to run on 3 cylinders. So I removed the plugs to check them and for overfuelling. The plugs were totally shot with the centre pin almost non existant. I don't know their mileage as I have only recently bought the car (59k on it now). A new set of plugs and no more light or misfire. Something to check before going too deep with the emission light problem.