I am in the process of fixing a problem with my daughter's 03 MCS. Symptoms were that it started running poorly, went into limp mode, wouldn't idle, check engine light and DSC lights on. Scanned ECU and found P0302 - Misfire on cylinder 2. Results of compression test were 150, 20, 150 150. Leakdown indicated air escaping from the exhaust so nothing else I could do but pull the head. Found a burned exhaust valve on cylinder 2. Holy crap these things are expensive to fix! If I weren't doing the work myself, it would be over $1500 for this job.
The machine shop said that they do a lot head service for the local Mini dealer. They said the factory exhaust valve guides are sloppy which causes them to burn valves around 70K miles. I can't help but wonder what I can expect now from my R56.