C & L Performance has done extensive dyno-testing on the 6.1 Hemi. With their cold air intake and the existing 3.5" throttle body, the air flow is 935 cfm. With a 4" throttle body, it increases to 1,015 cfm.

(Note- The cai is good for 18 hp without a tune or cat back).

See:

http://www.cnlperformance.com/hemi.html