SWIM, I would suggest two items.. First use a BMW diesel head gasket and second use M3 head bolts that are shortened for the M4x motor. These items are proven on Metric Mechanic's motors. They have had a few head gaskets fail and so far I'm the only one to blow the diesel gasket with a 29psi boost on pump gas which lifted the head off the block. Contact Barrie at Midnight tuning or I can help you with tuning 100% with no piggy backs or major changes to get a excellent tune |