The only fuel additives that will increase octane and power, and reduce KR are the ones made by Klotz. I have been using Klotz products since 1975. Most of their additives contain Nitropropane.
The Klotz Nitro Power Additive and CoOx Power Additive will show power gains in the dyno; I know, I have tested them and seen the results.
If you do not have a cat converter,
then you can use the Klotz HiTRATE Racing Gasoline Concentrate. HiTRATE will convert unleaded gasoline into leaded racing gasoline, but, it can clog the cat converter.
Klotz products are the #1 brand used by Go-Kart and Off-Road Motorcycle racers, and by gasoline powered R/C racers.
Also, the following link is an article from HotRod Magazine on the use of Nitropropane, actual dyno testing, and also what happens to an engine if you get too carried away.