Having read all the above, to make the long story short, I assume that you'd better keep the S54 in its factory home because as I read in another bmw forum:
The writer of the above (when he's back from business...) may explain the reasoning.
He has a point.
Ποιος θεός τα έγραψε αυτά?
Απλά ο τύπος κατέχει την απόλυτη γνώση!!!!
"There was s'thing of a sweet spot around the turn of the millennium, during which BMW produced two seminal masterpieces that have never quite bettered by their successors - the E46 ///M3 and the E39 ///M5" [BMW Car, 01/14]