Few things before we get to the numbers. First whoever does these for TAP bores them based on the inlet bore rather than the precision ground bore below. Easy to tell as the new bore/sleeve are offset approx .024" from the butterfly plate.

Next thing up is the sleeve wall thickness is thinner than the step thats left in the bottom of the bore where they bored over-size to accomodate the sleeve. There's a 1mm step that's in the bottom of bore where they stopped boring that protrudes into tha venturi full circumference around the bore I.D. The sleeve I.D is smaller than that bore which creates a step for air to hit/scatter and restrict flow. Would've been FAR better if the sleeve I.D. were left a bit smaller so that step was external to airflow. There's also that pesky inlet step which the sleeve creates by virtue of an added thickness. Would been nice had they done a little taper there to eliminate the step.

None of these things are major but they do add up and are cumulative. Other than that it's a very well machined piece. Nice fit and finish. Little too polished but I've been as guilty of that as anyone... maybe even more.

Flow is 364CFM (364.06 actual).

I would imagine S2 is cheaper and flows better too. :)