either the os 18 cvr or the epic 18 the os beat the epic in a test by 1 mph so its not much it pretty much comes down to wich one is less cost and wich one you think looks the best but i think think the os would give you more life also if moeny isnt a issue for you os also makes a rear exaust 18 the os 18 tm it would be a big difference from the cvr.