They have always been a fail. If done right they have no idea they have been gutted. This being a 2007 they aren't even required that year Audi designed and built this motor with them so they were added when not required. This motor doesn't use a down stream injector to inject diesel into the exhaust instead it has an extra injection cycle on the exhaust stroke which honestly is not a great thing for any engine it washes the cylinders down and dilutes the oil. Poor setup all around.