Cylinder Heads, pistons, other?

I'm going to replace the HG's on my new engine (1995 Legacy EJ22, swapped in place of a Gen 1 EJ25 in '97 GT) as PM and wondering if any significant gains from swapping heads. I have searched for a while this morning for some data on cylinder heads. I've found some good numbers for the SOHC heads but not DOHC.

I would love to have a good comparison on chamber CC and flow for stock heads for a '95 EJ22 SOHC vs '97 EJ25 DOHC.

Also, I hear (from WIKI, for whatever that's worth) that 97 and later 2.2 pistons have a slightly improved design that benefits HP and MPG about 10%. Would it be worthwhile to swap pistons? I drive about 2,800 miles a month so 10% = $$$$. I currently get just over 25 MPG and expect an improvement with new tires on monday.

Or - other thoughts? I'm used to driving about 300 HP domestics and while I enjoy the lightness of the subie, the handling, and the MPG, I would definately enjoy a little more go.

300 HP out of a H4 N/A Subaru engine isnt cheap, sustainable, realistic. Forget that idea. Second No gains from swapping heads and they wont fit the EJ25D bottom end.

THe benefits you read pertain to Phase 1 vs Phase 2 engines and a inter-pahse revision of the EJ25D.

In short stay with either the EJ25D or the EJ22E

Thanks for the feedback. I was not suggesting to get 300 HP from my Subie, just stating that I'm used to a lot more power and would like to add a little power in a way that would not overly hinder mileage.

The EJ25 DOHC heads DO fit on an EJ22 block, just in case anyone wonders. I put that together for my dad's car a couple years ago just because its what was around. It works surprisingly well despite at least a half point drop in compression. I haven't ever driven the car, but from the passenger seat it FEELS torquier than mine. But that could be that his is 5 speed and mines auto.

I still would like to see flow numbers for DOHC heads if any one's seen them...