Reading around a bit more you're right Richard. I must have picked up the wrong idea from some where on the net, I'm sure I read that it lacked the direct injection of the N52.
Am I right in thinking that the N54 just uses an alloy block with cast iron liners like the M54 (E46/Z4) rather than being Magnesium Alloy like the N52?
1st time I had the Z4 serviced by a local specialist I told them I had bought it as a keeper and they expressed the opinion that a well looked after M54 will probably outlive the later 3.0 engines. They had 3 E46's between the two of them, 330i, 330ci and a 330touring
Mate has just bought a E46 330cd which has been mapped to about 240. (I think it was the 203bhp originally?). Goes like stink but it just lacks a bit of the "soul" of the petrol 3L IMO.