Hmmmm,just plug it up and see,It stands to reason if you plug it up the engine will richen up,and if you pull the pcv valve off of the end it will lean it out.it's basicly a controlled vacume leak.plus having it hooked up does have other advantages that ramcharger has pointed out.If you had a meter to test the air fuel meter at the tailpipe you could see the diffrence with and without the pcv.but hey do what you wan't,the factory put them things on there to lower emissions,how could it lower emissions?besides look at em...what could they know??? :cheers: