Originally Posted by mapezzul
As for the engine- you can get 400hp out of the N55 but not using the stock intake system or turbo.
No, not in a reliable fashion. You may be able to get a dyno somewhere that reads 400hp with some aftermarket intake and modified downpipes, but this is far from the standard Alpina needs to adopt when marketing their cars.
Alpina tried that themselves when the N55 came out and there was the idea of integrating it into the B3S Biturbo. However, after a number of engines broke down during the testing process, this was abandoned. The N55 simply does not have enough potential to produce 400+hp and a broad torque band while maintaining the reliability and emission standards that Alpina is subject to.