I had my dct replaced due to vibration. The replacement is superb but I too get a whine when fully warmed up but only at WOT/full power and certain revs. I'm not concerned, it's 300+ BHP hurling the car forward, I'd be worried if it was quiet!
Black Sapphire BMW Z4 sDrive35i
Mods: HiFi Tweeters Stubby LED Halos & Front Indicators DVDInMotion SmartTop 313 BMW Performance Alloys LCI Repeaters http://goo.gl/PF4nSz