I recently purchased an 89 525i. Had a bad head gasket. when I took the head to the machine shop the guy went on and on about how " bad ass" this head was. He said it had been cnc machined, had over-sized valves, and appeared to have some sort of cam. The side of the head is stamped with: "BAVARIAN CNC". Engine also appears to have headers (which glow red when rpm's are held at approx 2,500 by the way) as opposed to standard type exhaust manifolds. Anyone have any info on what this translates to? Special work done on vehicle, or normal??