I noticed more roar from the rush of air being sucked thru oily wire reinforced gauze right away. Wasn't sure of any major performance increase, until I put a stock filter in while recharging my K&N. The K&N does make a difference for the money, and at under $50, the bad azz intake roar is well worth it. Your performance may vary depending on elevation, temperature, etc... But I got better MPG and quicker off the line response.