I am currently running a y8 block and head with hx pistons. hx has 9.4:1 compression, y8 has 9.6:1, so its not going to make a noticeable difference in that respect, but the y8 head is much better in the upper rpm. A mini-me using a y8 head is a great option for you. The block and bottom end of the hx and y8 are identical except for the pistons. You didnt mention whether you had the cvt or the manual tranny.