I would check (and probably replace) the rubber fuel lines from the fuel pump to the rail. Depending on how long the gas sat, and blend of gas (ethanol), the rubber fuel lines may have began to deteriate...leaving you with small chunks of rubber/trash in the fuel line to clog the injectors.
Next, I would check fuel pressure to rule out the pump. Just because it's operating, doesn't mean it's operating correctly. If you don't have a fuel pressure gauge, there are a few threads on here on how to build a simple and inexpensive gauge. I think pressure should be in the 39psi range, but double check that.
If the pump tests good, and you have good fuel lines, then you are left with the injectors. I know a few people that have had good luck cleaning the injector screens, but not me. I usually just replace the injectors.
08 Sportsman 800 Touring- EPI clutch turning 27" Mega Mayhems, 2500lb Polaris winch, front & rear SATV brush guards, front rack extender, 3 headlight Mod, Quadovator temp gauge, RAC Engineering reverse/ work lights, EBC brakes, Triangle ATV Stealth Snorkels, RDC radiator relocation kit, ATVtrailtunes split tube system, 12" Totron LED lightbar
08 RZR 800- 11 front end conversion w/ LED headlights, Dakota Digital dash, SATV +6 offset long travel kit, Rhino axles, 900XP shocks, 900 front hub/ brake conversion, QSC clutch turning 30" Carnivores, 3500lb Polaris winch, EMP 1/2 windshield, Air box relocation w/ custom snorkels, BoeschBuilt parking brake, dual Venom LED whips, 30" Totron LED lightbar, 6 1/2" Kickers & NOAM 10" subwoofer powered by NOAM 4ch amp
05 Scrambler 500- Polaris rear rack, Bear Claw tires, 12" LED bar, 2x3 OPT7 cubes (the wife's bike)
Grandkids- 05 Eton Viper 90R, 93 Yamaha PW50, 03 Yamaha PW50, 09 Kawasaki KLX 110- (They're killing me, lol)