Rich,Rainbird makes what you are talking about,I use hundreds of them in my orchard. They're called automatic drain valves,they open to drain water when the pressure drops below 3 psi. I use micro sprinklers with a very small,easy to clog nozzle,when the water turns off they drain the lines to prevent algae growth. Cost about $3 each with 1/4 NPT male ends, could be installed by welding a coupling on the metal elbow at the inter cooler inlet. Don't think they would be necessary in the desert west,but maybe elsewhere. Seems like the guys around Seattle would be the ones who need it most if it is in fact a problem.
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95' 25004X4,AT,Driftwood,Banks Stinger,Warn fender flairs and running boards(work truck)
95 3500,5 speed 3:54,BD E-brake,Driftwood,Banks&Psycotty,34,000 GCVW apple and tractor hauler(works harder truck)