I've had my car for just under one year. The k&n unit makes a big difference in miles per gallon. The city mpg has gone up by at least 2 mpg using the meter in the car. The longest ride I've taken since the installation was about 180 miles. The sound of the k&n has changed the car as well. The sound is of a pure ancient beast. At under 2k rpm the sound is hardly over stock. The sound picks up slightly from 2 to 4 rpm and is ever present from that point to redline.
Rating the K&N 69 Series Typhoon Intake System
Installation was not too difficult on my 2009n Scion xD. However, it did take to modification of the brackets and the air filter box to get the intake tube /filter to align. One other guy mentioned a problem with the PCV valve hose kinking; I experienced a similar problem. Performance wise it does provide a little more off idle acceleration and an increase in gas mileage. I am pleased with the performance. The fit, form, and finish of the Volant system is better. I wished they made one for my a