Originally Posted by fahr_side
No, the '10~ pistons are different. As I understand it the new heads have a chamber volume similar to previous models but with dual AVCS added. They're not the same heads as the GRB EJ257 ('08~ STi).
Therefore, the dish volume has to be smaller to come up with the higher compression ratio. I don't know if anything is different.
Didn't have an opportunity to post this sooner.
Yes, the pistons are different for the 2010-12 LGT. The crown shape of the piston head has been modified.
For the heads, slight changes. The combustion chamber has been modified. Cam timing changes for low range TQ; valve springs are different as well.
(Interesting that for the 2.5i non-turbo, the heads were changed to improve cooling and the pistons changed (shape and 26 gram weight reduction)