hi,possible valvetronic engine in your X5?i have X3 with similar habit,try to drive very gentle and progressive on throttle,i think you just need to adapt your driving style to cope with the variable valve lift.car pulls a bit slow then power surge.when you wish to shift up gear,hold or back slightly off throttle to allow engine to ballance,as though cruising at that speed ,then shift up gear.driving style needs to be same as using non synchronised gearbox (VERY SMOOTH)practice will make perfect,good luck.