I was a a gas station earlier this evening and the attendant was marketing a fuel injector cleaner. I want to ask, if the actually work ?

My candid advice is this. Basically, anything not mixed in my presence, I don't believe in it. Depending on the product, you may buy it and then inspect the efficacy using these two methods. First, when doing your next servicing, ask the mechanic to show you the head of the plugs to see if it is black or grey/silver. If it was black and after usage it changes to the former, then it is effective. Secondly, if the silencer opening isn't too dark, then you may consider it effective. Alternatively, get the mechanice to get an abro injector and caburator cleaner and apply it into the injector as appropriate. Regards.