I need ideas about the following:

When at a standstill or moving under 10 miles/hour, or reversing, there is a strong smell of exhaust fumes coming through the ventilation system. The smell stops when the ventilation is switched off.

This began after a service and mot 2 months ago. The lamba sensor had been replaced. The mechanic advised that it may be old oil burning off after having the cam cover gasket replaced. The smell has not lessened and is very intrusive.

 

I have the same problem and I'm looking for help. A6 2001 2.7T. Thank you.

 

Check the valve covers near the back for leaks. If they are leaking, oil will drip onto the exhaust manifold and it will get sucked into the cabin air when sitting still. Replacing the valve cover gaskets is not a huge job but you'll need to clean the oil that dripped out the back. A good blast with some "brake clean" will usually wash it off pretty easily if you can get a good shot at it. Clearance is tight back there.