Have the same unit in my VW. Needed something that commanded attention better than the "beep beep" anemic VW Bug trademark.
Note that the compressor needs time to spool up prior to sending the compressed air through the horns. So there is about a 1/2 second or more delay from depressing the horn to actually hearing it sound off...not good if you're trying to get someone to avoid hitting you!
I had a friend who was a stereo installer do the air horn route with his aftermarket alarm. Kept the alarm horn AND the air horn, and it sounded like something conjured up by Bill Nye the Science guy!
