kbstinky,
Never heard of any of BD'S brakes rusting up, not saying your wrong, but have never heard of it. I have had the spool valves getting dirty and then the brake wouldn't work right. They've changed the way some of the vents are, so they aren't so susceptable to dirt. Also the most recent ones I've installed. (just got done with one today) they are made to cycle on and off at start up. The worst thing on an exhaust brake is not to use it.
I can sell any brand of exhaust brake, but firmly believe the BD is the best of them all.
I wasn't trying to bad mouth Banks as some of their products are top notch. (I also can sell Banks if I should choose too) but they have had problems with their exhaust brakes. I believe there are some past threads on this site relating to this fact. tpitt