Vauxhall Meriva Exhaust Manifold Problems

I have an intermittent warning light which I have had checked out by a Vauxhall garage.It is the sensor ontop of the exhaust manifold which they say is sooted/carbon'd up and the butterfly vent isn't working properly. They say the sensor ca...

Car done 74,000 miles so not too elderly, but for several months has been erratic when starting up in that it will start but then jump along, a la kangaroo, until it gets going a bit more. Does this when engine or outside temperature hot or...