You can buy commercial cleaners from afe or K&N or try household degreasers like 409 or simple green. Just spray on and let soak for 10 minutes then rinse off the dirt form the INSIDE out only so you don't push the dirt into the filter. Use gentle water pressure, not a spray nozzle. Let dry in the sun and DONT use heat or hair dryer to dry. You can gently swing the filter to get a little water off or try a wet/dry vac and suck some of it off from the outside. Then when its all dry, spray a good coating of air filter oil on it but don't get carried away. You don't want the sensor or turbo getting oil all over them. This has worked for me for years, it should work for you.