I'm told it's because it creates a vacuum where that breather enters the back of the TB. Were one to relocate that upstream of the intake restrictor, it ought to reduce that oil consumption cause by the suction on that hose. We shall see, I picked up a 5.3 and am slowly gathering the bits to do the swap. I don't think I want anything other than a stock y pipe for ground clearance. I know on my truck that ditching the 1 7/8" pipes off the manifolds for some dual 2.5" pipes made more torque from an idle up, so I'm hesitant to think that choking the flow will really boost torque. What I really wonder about is the difference in torque produced by an x pipe vs a y pipe.