My 2013 VW Tiguan began running rough and the check engine light came on. The dealer did a 100k service and replaced plugs and a couple of coils. It ran fine for a few days and then the problems returned. The dealer said it would cost $1100 to manually clean the carbon off the valves. I looked around and 101 European had a treatment to clean the valves, cylinders and injectors without taking the engine apart. It cost less than half the dealer estimate and the engine runs so much smoother. I’m definitely coming back.