I have just experienced my third case of the issue with the Ford V-10 Triton. (2005) First time we were parked for a few days after experiencing low power and RPM, limped into a park . Next day all was fine. The second was in a Mississippi rain storm we experienced another incident and again limped to a Ford dealer who after attempting a computer analysis of the engine he opened the Air Cleaner canister and found the air cleaner filter wet and collapsed at the base, New Air cleaner and on our way. The last incident this past week convinces me that the design of the air filter intake (pointed to the ground behind the grille) is the cause of the water intake causing the air cleaner to block engine air and a resultant engine loss of power. All three of these cases occurred during a hard rain at highway speeds. Dangerous situation as 20- mph is max down hill and near dead engine stall uphill. The indication is a slight "humping" of the coach which feels like transmission shifting problem that increases in frequency and severity as the water continues to collect.
Suggestion to all: Get off the road immediately when this condition occurs. (My wife said she felt like a truck target) Removing the air cleaner does not allow the engine to run. Take the air cleaner from the canister and dump the water out (I got two cups) and if possible using a hair drier and get the fabric as dry as possible, head to an auto parts store and obtain a replacement filter.
I have now seen other forums on this issue referring to modifications but none of the items listed are available. I suggest care in modifying the intake port as this may affect engine performance.
My best suggestion is to carry a spare filter and at the first sign of "humping" get off the highway and replace the filter. 15 MPH on a rainy freeway is super dangerous!!