This is all the crap Walt scraped off my evaporator coil this afternoon. I'm guessing that's probably 15 years worth... or possibly 30 if they didn't clean it when they replaced the furnace.
Above is how the coil looked after scraping the dry crap off. It then got a nice coat of cleaner/foam and was closed back up. The condensate ran brown afterward. I'd have to say this must help.
It's running now. We'll wait for the sun to go down and see how it does.