My 2008 Audi A6 Quattro is at the mechanics, it was in 0 degrees Fahrenheit for a week. When I started it, it was knocking really bad. All of the passenger side cylinders have a reading of 300 psi, all of the drivers side are reading 150 psi. all are also leaving fuel in the cylinders after being turned over. Any suggestions? It was running fine prior to getting this cold.