B18C1...

Stock form is better for boosting than ITR...

If you use ITR pistons with the GSR motor then you make more power than the actualy Type R due to higher compression.

Higher avalibility of parts..

H22A has more displacement, but dosent respond as well to mods, as well as the fact that there are LESS OPTIONS for parts.. As far as boosting goes, H22A hates cranks