Something may be making it rich. Make sure injector isn't leaking.Does the canister have liquid fuel in it. Map sensor vacuum good? Low vacuum to map or bad map. Pull line off map and make sure you have good vacuum. That port at throttle body can get clogged with carbon. Fuel pressure regulator problems can raise fuel pressure and cause rich condition. Also I have seen restricted fuel return lines cause pressure to be high. If the lines at the tank were ever replaced and not routed properly they can get pinched. Fuel selector valve not switching completely could be a problem.