Are you referring to the vertical piece of particle board that butts up to the cab of your Bronco? If so, my FWC also began to sustain water damage to this material. Once water gets into it, it swells up and looks like crap. I ended up catching it early, totally resealed all sides of it (especially the edges under the trim that are not painted), and installed a white plastic veneer over it. I also did this to the underside of the cab over portion as well since it is also made with particle board. I got the plastic sheeting from Home Depot. Its made of recycled plastic and has a nice texture on it. Its like 1/16" thick. Its meant to be a durable, water proof, stain resistant veneer for walls in industrial/commercial facilities. I used Tough as Nails Professional Level adhesive with the 8X high tack to glue it to the particle board. I applied it with a caulking gun and then used a trowel to spread it out in a nice thin layer. I ended up removing and then reinstalling all the edge trim so the new veneer actually runs up beneath the trim and looks like a factory install. I don't know why FWC ever decided to use particle board on an exterior surface. I believe they stopped doing it a long time ago after many complaints. Hope this helps.
