Additives are a waste of money in E-free gas.
I own two outboard motors, two lawnmowers, a generator, a pressure washer, a leaf blower, a chain saw and probably something else I can't think of. Not one of them has ever had a fuel-related problem (or any other problem, for that matter) since I switched to E-free, five years ago. I can walk out to the shed and start any one of them in two or three pulls, any time, every time.
Nothing wrong with using additives if they make you feel good, but that is the only benefit they provide in E-free gas.