the XE pistons are forged and can take some hammer, but the problem u have is in an XE engine with turbo rods vaux people get away with runing big boost for some reason

but cause there in a zetec they wont be same,
and u NEED to check somthing, cause very zetec turbo ive had to strip down from a failure for people doing cheap conversions vauxhall pistons spin them selfs on the little end! and the little end bearing is always tight in the rod, if that makes sense,
ive seen no end of oval gudgeon pin holes in pistons because of this,

if it has been prepper propperly mate and engine built and the above mentioned was sorted, then just run it high comp, make sure u use a focus RS head gasket, some ARP's and dont skimp on having a MAP done u could have alittle poket rocket as high comp turbos = no lag, lotts of fun!!!

jus a pig to map and dont expect BIG power, but plenty of torque