"Back in the day" a high idle could have be indicative of an air leak. Check anywhere you could have developed a leak. Head or base gaskets and any intake gaskets. An air leak could also be found at a torn or compromised crank seal. Old school guys would spray water or some sort of cleaner around the aforementioned areas while the motor was running. When you find the "bad spot" the idle will come down.
Also, be sure to check that cable again. I've seen instances where the cable will pull out of it's sleeve near the carb. and become "hung up." Good luck.
