Originally Posted by Racehead

Todd a possible explanation to that could be that when you replaced the composite intake with an aluminum one you increased the airflow thru the intake reducing the psi slightly because of the increased flow. You also simultanously went from an intake that did NOT readily transfer engine heat into the intake air ( composite ) to one that DID easily transfer engine heat ( aluminum ) into the intake air. Hotter intake air = less power.

Just one possible explanation