Also if you're not already doing so check the float level using the clear tubing method rather than using the static measurement with the float bowl off. If it checks out ok drain the float bowl and recheck it a couple of additional times just in case it's hanging up intermittently. If you have it apart again measure both floats and make sure one float hasn't become tweeked higher or lower than the other, cuz that one will make you crazy.
Just my .02. Sometimes you gotta figger out what it ain't