I was wondering the same thing !! I believe that the 4.8i engine would gain at least 20 hp and thats due the twin air intake .

__________________
08' X5 4.8i with all the options,aerokit,25mm rear wheels spacers,meisterschaft Exhaust GT racing performance level,Hamann lowering kit,LUMMA headlights eyebrows.

MY X5 PICS