There are alot of effective solvents you can mix with your gas. STP, Bardahl, Seafoam, etc carb cleaner, fuel injection cleaner, fuel system cleaner are all pretty much just naptha, kerosene and isopropyl alcohol. The kerosene and naptha have the same btu/liter energy content. I use only naptha in lawn mower, snowblower and outboard for varnish removal, 3 oz / gallon. Naptha is cheap at $9/qt compared to $6/ 1/2 pint for STP et al. Point being, MEK or other solvents can be added to you fuel to dissolve deposits if you are still running pretty good. That lawnmower/snowblower surging you get with clogged jets dissappear in 1/2 a tank of fuel. These solvents probably have a lower octane rating (octane is an 8 carbon chain and these solvents are 3 or 4 carbon chain, I didn't check) but a few ounces in your 91 octane is not going to be a detonation issue with a reasonable C/R. If you suspect that the liner is coming apart and going to your carbs this might help. If you have used these additives and your liner is failing, this might be the cause.