For power, the TTI seem to work good for a shelf Abody-Bengine header but if you are ever going to compete in SS...you'll need a custom set. FWIW there was a company advertising a shelf header for this application on racing junk. I have no experience in the 'service access' that the TTI allow and when a custom set is made they definitely can be done in a way that saves time and grief along with making more HP.