All I can say is that whenever we ride the dunes the first thing we do when we're done is powerwash the bikes and clean the filters before we put them to bed. Usually after a muddy or real dusty ride we do that anyway...maintenance is key. Be sure to check out the end of On Any Sunday :-)
You and the bike will end up with sand in places you'll be amazed that the sand got to. So remember when you clean up and remove the sand from your cracks and crevices that you need to do the same for your bike.
I did the Wildwood race once. Never again. Costs a fortune to ride for 15 minutes. If they cut your moto to 2 laps make it 9 minutes including practice. :debil: