I am building an engine for mine (04 rs) and I am using the turbo gaskets. I put them right on top I non turbo ones and the are perfect fits. And I figured the 2.5 sohc would benefit from the compression bump. And really the differences in thickness will barely change the ratio anyway. I would say go with the factory 04-05 sti gaskets. That's what I'm using. Hope this helps.