I know you are relating the lack of 'GO' on your recent radiator problem (who ever came up with the idea of plastic for radiators anyway) But I wonder if your fuel filter isn't getting loaded. adding the injector cleaner has been known to do two things: loosen up all the varnish and crap in the gas tank thus loading up your filter and 2. causes havoc with spark plugs. they lose their insulation for some reason. It has happened twice to me on my motorcycle (a 4 stroke) I'm chasing one problem only to have it combined with intermitent plugs.

I can't see your (now) florescent green/yellow engine being harmed by antifreeze hitting it.