We had the same problem on our 2001 Adventurer on the Ford chassis. The initial fix by our local Ford garage was to turn the intake snorkel to the side and shield it with a rubber flap.
After the initial fix we didn't have any more problems. However a couple years later Ford came out with the TSB and the "snorkel" kit. Since our motorhome was still under warranty the Ford garage installed it at no charge.
There don't seem to be any new snorkel kits available from Ford. You might get lucky and find one of the few remaining as previously mentioned or check out salvage yards. If all else fails you can do a fix similar to the original one done on our motorhome.