So Ford goes to great lengths to promote turbulence in the intake track. The 1999-2004 PI heads have a quench pad in the head, the 99-01 heads are supposed to produce an air tumble effect (hence tumbleport heads), and the 2005-2010 3v heads have a butterfly valve in the intake tract. That being said, if the spacer induces turbulance, it would be long gone once the air travels through the intake plenum and into the runners. Besides fuel doesn't get injected until right before the intake valve. (So make my plastic intake as smooth as glass.) The spacer is pure snake oil.