you can have a rich idle and a lean WOT. 2 dif. parts of the carb. what kind of carb. do you have?

"but wouldn't that only tell me if the burnt valve is on the intake?"
this is a ? you had before and no one answered it. this would tell you the burnt valve was on the exhaust, not the intake. if the intake valve was leaking then you would hear comp. blowing back up through the carb.