I can say from experience. You have clogged injector(s). The bike should idle smoothest with sync screws closed more because the idle sync screws affects mixture making it richer. And the only pour in the tank cleaner that might work is Yamaha “ring free”. Option 2- Removing the injectors and a “proper cleaning”. Seafoam= joke , mainly a carbon remover by being difficult to burn, it has no solvents. Fyi- morgan carbtune’s hoses are WRONG size for FJR. The hoses should be 5/32. Take the 3/16 and put an adapter to 5/32. Also confirm the sync caps are not loose or cracked. I use silicone caps. Fact: TB#3 was set at the factory for proper emissions.