its not only mk5s though, i find that i rarely get any response from most mk5, mk4 & mk3 drivers and usually get ignored by most aircooled stuff too (which surprises me as you must be an enthusiast to own a beetle or camper etc, i love aircooled but always get the impression that they dont like watercooled very much). This is just usually tho, there are exceptions.
The majority of mk1's mk2s and Rado's flash or wave.