My parents new '71 383 auto (3.23 open rear end) Road Runner had the "air grabber" hood. It ran about 15.00 (showroom stock) in the quarter mile. Opening the "air grabber" apparently had no effect over running with it closed. I believe it is a very difficult proposition to accurately test the results of any "cold air" induction system. The difference with/without seem to be minuscule at best or generally downright impossible to determine.