Actually Gents, there is an oil gallery plug on the rear of the EJ's that is used for oil temp sensing....Sandwhich plates are unreliable and leak.
Look between the turbo & inlet manifold for the hex keyed plug.....that is the rear oil gallery plug......
You buy the same plug that holds the oil pressure switch (for $13 from a dealer - 11024AA210 Plug Main Gallery), replace the plug that is a blanking plug, screw in your 1/4 bsp sensor and it's done.
It's the factory location for oil temp as used by
WRC cars.
Google Subaru oil gallery adapter / oil temp sensor and you'll find what I'm talking about.....
This is the adapter:
This is the rear oil gallery plug with a temp sensor in place of the blanking plug:
How to PDF :
http://www.j-spectuning.com/installs...OilGallery.pdf