Hi im currently rebuilding my Z20LET engine as im getting a Garrett GT turbo put on , its going to cost me £600 to get the cylinder head gas flowed... I donít have to do this but im thinking if im spending all this money I might as well do it as long as it makes a difference!! Has anyone had there head gas flowed if so is it worth the money?? Also is it the same as getting the ports polished, or is that something different? Any input would be grate!