On my E92 335D, sticking it on cruise @ 70mph i get 47-49mpg.
But driving it in town with a lot of stop start and pedal to the metal, it can go as low as 20mpg!
I too will be replacing one of the stats soon.
Turbo Dynamics Hybrid Turbos, Wagner Intercooler, DPF Delete Pipe with Sports Cat, Ecotune custom map ~ 422bhp & 618ft.lbs
Ohlins R&T with custom Swift rears