My other 1303 GL

[H2OSB]

That's what I suspected(mock up only). Though I believe the WRXs here in the states originally came with boosted, open deck EJ22s, like your mock up block. My LegacyGT had an EJ255 which, like the EJ257s in the U.S. spec STIs are semi-closed deck. I don't know much about the JDM spec engines you guys get in Oz. I was only asking because I ASSumed with the power you make in your 1303 you would start with a semi-closed deck, though I don't even know if it's necessary.

Have you ever seen one of the closed deck blocks from the original 2.0L(or was it 2.2L) Subaru turbo engines? Supposedly They can take some serious boost.