My 2012 CS has 13k miles. Last week the "Reduced Engine Power" Warning started flashing on the display. I took it to the dealer immediately.
I bought the car in August and it's been back to the dealer four times.
They kept it for two days and told me they couldn't replicate the problem and assumed I had either: a.) put in non-premium gas or b.) got bad tank of premium from the local BP station. My last four cars have required premium gas so I would not make such a mistake.
The next day, I was driving to the airport and the "Reduced Engine Power" warning and chime began to go off and on again every few seconds like a fire alarm. I called the service manager (who is a great guy and gave me his cell number.) and told him I was ready to "give this piece of junk back to Porsche."
He had one of his porters meet me half-way to the airport and swap my Cayenne for a Panamera 4.
Now I just wish I had bought a Panamera. The car is awesome. I drove it through a snow storm and it stuck to the road like no car I've ever driven. It handled snow covered roads as if they were completely dry.