I upgraded from stock to the Pipercross foam-type air filter which fits in the Coopers air box. It comes with oil so you can clean and re-oil it for life. I noticed an immediate improvement in pick up and smoother shifting. Alas, some cool people bought me a whole new intake for the holidays, so I'm selling the Pipercross. You don't have to make any modifications to your car, just replace the factory air filter with this one. Paid $50, selling for $30 (shipping IS included)- comes with bottle of oil that will last you a lifetime. Send me a personal message and I'll get back to you ASAP.

Thanks, Tracy