1989 Dodge Dynasty Lack of power

I just bought this 89 Dodge Dynaty yesterday. It belonged to and older couple that can't drive anymore.Its in really nice shape. The car sat alot in the garage and got little use if any the pasted two years. If I push the accelrator down past 1/4 she stumbles and falls flat on her face. If I hold the throdle wide open in nutreal it won't rev up enought to even worrie about causing engine damage from over reving. it starts hard espicaly after it's warmed up. It feels like its running lean, some times if I push it to hard it will back fire through the intake. I put a bottle of injector cleaner in the tank last night. Do you have any other ideas what this might be? Thank you. Paul