So im assuming the 3.5" isnt necessary at all. So, im thinking then 3.5" collector through 3.5" cutouts, then into a 3" X-pipe and out the rear with the round 17223 round ultraflow placed where? I was going to place them where the factory fuel tank was supposed to be. So they are closer to the rear end of the car, UNLESS they would sound better placed just after the X pipe.