BMW Z4 sudden drag in top gears

[MyMidLifeCrisis]

My friend has just bought an BMW Z4 SE '07' model. When driving at 60-70mph in 5th/6th gear, he has experienced a sudden drag, as if the brakes have been put on gently for a second (not a loss of power). Has any one got any thoughts

[8Tech]

What engine?

If its a petrol, then pencil coil failures are common.