Spacers? Do they work??? The verdict is still being debated but for some people they do make is difference and for others not so. Either way, no one is going to force you to get one. How do they work? We are NOT going to tell you it swirls the air or generate a vortex but a spacer does increase the air volume in your manifold and this does help in the older style manifolds ('99 and older). If it doesn't swirl the air, why are your spacers cut for that? The reason we added the swirl cuts it to increase the spacer's volume without weakening the spacer. Our spacers are bored out to almost 65mm in volume without weakening the spacer.Hardware and gaskets included.