Ea's have a giant swirl vane cast into the head which will increase compression on a 4.0. I have been told if you remove the swirl vane it will lower the compression on a 4.0 to about 8.3:1 making it good for boost . Also I know of two people who have machine the tops of the ACL RACE pistons and used them for boost, one for 270rwhp at 12psi and the other for apparently 400rwhp.

Virtually the ACL RACE kits raise the compression slightly without any milling or decking.

well i wasnt really worring about raising my compression, its just that im building a new engine, including new pistons, so i thought while im at it i may as well throw in some flat tops, so condidering that is it realy worth me spending the money on the acl kit or what? what pistons should i get?