well i think its at the top end when your needing more air, the more boost you run the smaller throttle body will slow it down,i know that i picked up 4cfm by changing the throttle body,if you have a t28 it stands to reason that you need a throttle body simular size to what car the t28 came off and i'am sure it would not be running a tiny s12 jobbie mate, the s12 tb is good for the standard boost on a t2 and thats it, its very restricted, if you are fittin an afc, you could do with fitting a larger afm as well.
