A stock 16v block yields a volumetric compression of around 10:1 in the various permutations of the 16v motor, which when using a turbo isn't ideal. The ideal compression ratio is anything between 8:1 and 9:1 and there are several ways in which to achieve this.

Low compression pistons
This is the most obvious option for lowering compression and has the added advantage of the piston being forged aluminium rather than cast, and therefore more heat resistant and less likely to melt if a poor engine mapping leads to detonation (pinking).

Stacked metal gaskets (ABF head gaskets) or spacer gasket
Stacking or spacing are the cheapest options for lowering the CR, as you are retaining all stock components, but be careful with the timing as the extra height of the block means the timing marks will not line up. It may be worthwhile using a vernier CAM pulley to correct it.

Offset bushing
This is a means to drop the piston height slightly. This is acheived by using a bush to offset the little end by using a smaller pin and a bush to offset the centre of the little end pin and thus dropping the maximum height of the piston.

Machining stock pistons
It is also possible to machine the piston crown down to reduce the compression. This method is not recommended as you will be reducing top-land area of the piston, which makes the piston less resistant to heat.

Combining 8v block with 16v head
This can be done with the 8v 2E or ABA blocks and any 16v (PL, KR, 9A) head.