I had a similar thing happen to me before, it was an air leak, that only sounded when the supercharger kicked in as there was a lot of air pressure, sounded like a fog horn so may not be your problem but worth a look.....
As you look at the engine, to the right (port side) of the air box you'll see the air pipe, with a rubber ducting held by 2 clips (The ducting is only a few inches long). This is where the air was escaping from on my engine... only took 5 mins to fix
Other than that, did you check your belts? I found that the KAD32 eat's belts, but mainly the CIRCULATION belt (which is the most inside one and most annoying to change!). When the engine is off, check tension of all belts, esp this one. If it's just loose, tighten it up, if it's knackered then just replace it