Just wondered if the dme was stock Bmw for the engine in our beasts? If so I wouldn't imagine it wouldn't imagine it would be too much work to get its big brother the m62b46 in - has anyone done this before?

Not me but first i ask why. Isn't the fuel economy low enough with the 4.4?

This is true but in the x5 it's not much worse and it's 350hp - if your on gas anyway you wouldn't notice a great deal

Theoretically it should swap out. I thought RR tweeked some things in the oil pan or sump to handle steeper inclines. I could be wrong. Xoutpost might have more info on this.

Yes I believe the 4.4 lump ihas several differences to cope with inclines and some other differences which I have forgot about but it is not a straight swap.Why would you want to do that anyway?more power?You could spend the money modifying what you have got with a sports exhaust ,management tweeks or even have the heads reworked .