I finally have my Corsa Track system completely installed (with 3" RT h/f cats). I have 3" Vortex cones just in front of the mufflers. The Corsa track sounded good (not too loud) on the highway, but very loud/harsh upon start-up. The Vortex cones have taken some of the harshness away in all conditions. (My former B&B system was louder than the Corsa with cones, but quieter than the Corsa w/o cones). I like the sound -- it's different (it burbles kinda like a Harley) -- but -- it might just be my brain, but it seems like there's also been some HP loss. I'll probably leave the cones in ... but there's the report on Vortex cones.