I remember reading that when these cars left the factory the engines were sprayed with some chemical that served as a protectant. This protectant was suposed to be removed by the dealer when the car was preped for delivery. But on many of the cars they either were not removed properly or not at all. I notice that my car that I just purchased has a valve cover with the motorsport letters yellowed. I have tried removing it and I have had partial results. I used a quarter to chip at the yellow film on the letters and followed that by some metal polish. There still is some yellowing left in tight corners. I am wondering if any one else has tried removing this film with good results. What method is the best to clean these valve covers.