The VF22 isn't necessarly better. The VF22 can achieve 310whp with a good tune. However, even though the VF34 can only achieve about 280whp with a good tune, it spools up considerably quicker than it's older brother with its newer roller bearing design. The difference is about 500rpm give or take. Of course, it you get a port and polish, it would also change your spool up time.
Neither of these turbos will get you the whp you want. I'd consider looking into an 18g. This thread would probably interest you.
EDIT: sorry, my post was based off a 2.0L, i have no idea what it would be for a 2.5
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