If you're worried about O.E.M. look for possible state inspections then the TVT would be the way to go. Because cost was an issue for me, and I'm not racing our 6, I went w/ the single NW but with the bigger, better flowing Xtreme K.&N. filter. I have yet to see a comparison of how much better the dual setup actually does on the dyno, compared with my setup. I'm guessing very minor. But if you're drag racing and can get even .1 or .2 seconds off your time, then it would be worth the extra cost. My .02 cents.