I have a 2005 GTX that acts like it has a plugged injector. Symptoms are similar to a dirty fuel filter. If I go full throttle it sputters then catches, recently it keeps better and better, but ot quite a peppy as the other VTX same year etc. Been running fuel injector cleaner(extra dose) and it is better. Fuel is fresh, however they sat for a year, siphoned old fuel and put fresh 91 octane. Any ideas?