STi heads > WRX heads

An intake mani will make the biggest difference when close to head efficiency. I'm not arguing semantics with you about who made what and i won't argue that claim because anything is possible with the right setup.

From what theory tells us about what a STi head will (bench) flow is that 650hp is about it without extensive modification, alternate fuels, or improving volumetric area for moving air, or making the head plain more efficiency.

As the new build progresses it's getting a lot more expensive.
The last motor i could only get about 530s out of her. Turns out the quench area and comp ratio weren't ideal and it was really prone to knock so i couldn't run shit for timing. It's under the knife again with some custom quench pistons and lowering the comp a cunt hair.

600+ is a big task....a lot say it's easy to do, but they're usually owners of shops. This is my private weekend car. I'm not sold on ridding of the 6262. I definitely don't want a HTA35R.
I might try the PT and if its no bueno then teh HTA86 is looking mighty fine.