I have a Holley 750 vacuum secondary 4160 series carb on a 360. The carb is roughly 2 years old. The engine developed a miss at high RPM. Then it got worse. After replacing the whole ignition system I found the problem was the carburetor.I took the fuel bowl and metering block off of the carb and found about 35 chunks of metal , im talking big chunks of metal.The fuel bowl side of the metering block was corroded and flaking metal like crazy.That is where my miss is coming from. The ports in the metering block are clogged with this crap. A guy at a car show told me to check it because he had the same problem.He said several people he knew had this same problem. The only thing I can think of that would cause this is the ethanol in the gasoline. I beleive the ethanol has a corrosive effect on the metal the carb is manufactured out of. Guys pull the fuel bowls off of the carb and check them before this crap gets sucked into your engine.