Highly recommend Turner Test Pipes (primary cat delete) - see my review here - http://www.m3post.com/forums/showthread.php?t=379286
This definitely retains the closest sound to OEM, and no smell
I'm seeing what feels like 10% increase in low-mid range torque and 5% increase in peak power. iPhone dynolicious reports peak Gs in 2nd gear of 0.56G with turner test pipes, vs 0.50G with stock exhaust. This is with a Powerchip tune.