This sounds like bullshit to me. they want to put a thicker head gasket to lower compresion in order to stop you pinging. but what about the loss of hp you are going to take. which easily could be 5 to 10% power loss depending on how thick they go with a new gasket. They should take the X5 back and give you a new one.

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Dinan M3

2006 X5 4.4i Sport Current Vehicle
2006 CLS 55 AMG Current Vehicle
2010 FORD F-450 King Ranch Current Vehicle
2012 GL 550 Current Vehicle

1999 M3 Dinan S3 SOLD
2001 M3 Dinan S2 SOLD
2002 M5 SOLD
2004 X5 4.4i sport SOLD
2007 335 XI Lease ended
2009 E92 M3 SOLD