Originally Posted by Alpina_B3_Lux
Alpina do not use the OEM pistons but install forged pistons from Mahle, which allows them to lower compression without sacrificing power output. Those pistons are rather expensive, though, I got a quote on them for around 2000 EUR.
Thats what I said, Mahle are very expensive when you consider someone like CP will machine a set to spec for a Grand. 2000 Euros is actually a good price for a set of genuine Mahle pistons if that includes taxes.
The OEM pistons will already be forged (even the "old" S54 had forged/part-balanced pistons/rods/crank) but Alpina choose to lower the CR to play extra safe.
If you lower CR you always loose power, the only way to make it back is raise boost or advance timing but obviously the lower CR allows this and a little more safely.