High how? Look @ people like Aaron34, Tangomatt etc making 400-415rwkw with 2.8ltr's on 20-22psi with -5s
Im @ 365rwkw on 19psi with timing pulled out. Jack & Snowy both made 370-380 (-5, 2.6ltr). I've posted the graphs up before.
Don't forget we aren't talking stock motor results. They do indeed sit around the 350rwkw marker on stock motors (hence i think -5s are a bad choice) - so no argument there from me at all, totally agree.
Built motors with some porting and so on make more in almost every case.
-9s and GT-SS are identical - 2530 and -5 are not.
2530s are bigger, and will make more power. A 3ltr, running more boost again (when you factor things in), evidence would suggest it should be higher.
Could be exhaust restrictions, or perhaps just a conservative tune or something else entirely.
It'll be good to see when Paul & Steve get their -5s tuned on 3ltr and 2.8ltr respectively. That'll hopefully provide some more results.