Due to the very efficient chamber design...but more importantly the computer. It will help with idel and part throttle characteristics. What is a huge street cam in an older set up can be quite mild in a LS1. You can go to a very big cam and still get good gas milage with an LS1 as well. Vince still gets in the mid 20s for gas milage in his 550+ rwhp 408 LS1. Thats due to chamber design and computer.