1996 Dodge Truck Power and performance

Hi, My ram seems to be lacking power, should the button for the o/d be turned on. It is unlit so I assume it is off. Have changed dist. Cap, rotor, plugs wires, plugs,
have installed airaid cold air and throttle body spacer, have installed a flowmaster catback exhaust, have changed oil and filter, running 10W-30 Synthetic, have changed transmissin fluid and filter, have redone front brakes, tierods, track bar, and ball joints plus wheel hubs. Still. It seems like it is lacking power. When I step on the gas, it takes a gradual incline to get speed up, on my other truck. When I step on it, it spins tires but not on the 96 with a 5.2. Is there anything else I should check to get a better throttle response, \Thanks