I'm not surprised that the octane boosters reduced HP. After all, higher octane means slower burning fuel, and the octane booster itself has few BTUs/gal than gasoline. For those additives to work, your engine must require higher octane. If the fuel has the correct octane rating for the engine, adding octane is counterproductive.
Some fuel additives are beneficial. Chevron Techron is a safe, effective detergent. If you live in California you probably don't need it, but if you live in some other state it can make a difference in performance over time. (If you live outside CA make sure your gasoline is
Top Tier rated.