I use Redex when getting the bike back on the road after winter. The bike has usually been sat out in the elements for 3 months, with the carbs full of old fuel, which I'm sure must evaporate, plus whatever condensation there is about, at least there is loads of water sat around the top of the engine. It always runs lumpy.
Redex seems to make it run crisper.. well on all 4 cylinders at least, it also seems to burn the engine hotter. When you talk about before and after photo's, if you've ever taken your head off after using a fuel additive you'll see the piston, spark plugs and valve heads all have a dry red tarnish on them. All bare metal with no black deposits, I would assume the valve seats look the same also.
Fuel additives definitely do something!
I remember a few years ago having an old car MOT'd. The garaged failed, then passed the car on emissions. When I asked him how he got it to pass he said he had just put a bottle of fuel additive through it.
Anyway, each to their own. Some people on here need to calm down a bit.... you'll be back later asking for some help, advice, with a problem or wanting to borrow a tool. Then your tone will change!...
