I agree with the other review here. So far I haven't noticed a big increase in performance, but the sound quality is significantly better than with the standard box. I think it's quieter at idle but makes a raspier sound at full load, especially when VTEC is engaged it screams. Haven't noticed any rumble in the exhaust noise either. I also noticed a slight increase in gas mileage, maybe 1-2mpg. Since the S2k was built to be a near-perfect car, it takes a lot of money to increase performance, so