I have a k&n cai want to take adavantage of the added airflow. How much hp will a 52mm bbk throttle body and airfoil add?

 

At this point that same money would be better spent on springs and rockers, the stock TB is fine for a stockish motor, looking at a cam before replacing it becomes even maybe worthwhile and not necessary till heads and cam. Headers would also be money better spent as would pcm reprograming, custom work is cheaper and better than Hypercrap and the like..