Congratulations for finding this issue. That's really an unusual one.
I really don't want to be that guy, but you still should be concerned what is the real problem with your car. Why has there been a spacer installed, which would never be necessary on a healthy engine? And what caused that amount of carbon buildup to block it? This is definitely not normal. Your engine is either burning too much oil, has one or more bad injectors, low compression from worn piston rings and/or burnt exhaust valves, or you are simply using bad quality fuel. Or something else I currently don't think of. Whatever it is, your fix is most probaly just temporary.
