I did this without knowing there was an "official" modification. I did mine a bit differently from the Gotts process, but it's probably just as effective (and not worth the hassle of changing it now).
I removed the snout from my stock aircleaner, and used a piece of ABS pipe (3" IIRC) reamed out with a Dremel sanding drum a bit to fit over the end. I applied some thick foam weatherstripping the side of the engine compartment around the hole that leads to the fenderwell to seal it up. I didn't need a coupler with this method, and already had the pipe and wx-strip lying around.
Andy