my head is with Karl as we speak, i'm having the Stg1 which is basically a 'new head' , it'll be re-faced, multi angle valve seats,new guides, stem seals and a light port on the inlet throat.

he'll do whatever you ask him too, but of course he'll advise what he feels is best for your spec. the light porting he does i'd imagine isn't necessarily to gain performance as such, just to improve on the standard design, it will rev better higher up but i doubt you'd see much power gain. if you do want to go over 400bhp then you'd need different cams and maybe turbo and it gets expensive then as you'd probably also need double valve springs etc etc etc

The sky's the limit really, just depends what your target power is