Alpina models tend now to use turbochargers and recently have been using the twin turbo engines and tuning them rather than using their own engine block. In the E53 the 4.8is was very close to what an Alpina would have been so there was no room really for Alpina, Aplina is really a half way house between the M/// cars and the regular range.

Maybe once the twin turbo petrol engined X5's we may see an Alpina X5, or maybe a diesel version. Alpina have recently released a D3 which is a tuned version of a 320d which is priced below the 330d but offers simialr performance and has the Alpina features.