[bwood]

With an extended warranty, you are, for the most part, at their mercy. Burnt valves at that mileage may also point to other issues that they should explore. Also remember that if the dealer puts it on, reguardless of your extended warranty, it should have a 12 mo/12k miles warranty as long as it is a OEM part. Make sure they are very clear with their repairs and they explore all possibilities. The code you listed, P0300, is multiple cylinder misfire and can be hard to locate the cause.