This is more of an FYI for an inexpensive fix. The WOLO horns went bad on the QP. I just had a buzzing compressor noise. You can order new horns directly from WOLO or you can walk into Advance Auto and purchase them for half the cost ($24.00) badged as FIAAM and the set includes the air horn compressor. Just use a screwdriver to pop off the WOLO black top bracket on the compressor and reinstall on the FIAAM compressor and you are good to go. The horns come off with a simple twist of a screw. The whole replacement, including grille removal took about eight minutes.