IMHO
Octane Booster - is water. Here in Slovenia we have a lot of it in pertol sold on gas stations.
Fuel System Cleaners, Injector Cleaners - is white spirit ususaly mixed with diesel fuel. Ultrasound injector cleaning is better.
Oil performance additives - used something from that on my lawn mower with B&S engine. Engine seezed at the end of the year. So no thanks.
At the end: as David C said.
