98 Jeep Cherokee Sport inline 6 cylinder low rpm misfire?

My 98 Jeep Cherokee 4.0 misfires on cylinders 3 and 4 if im going under 1500 rpm. I have change the plugs and wires. Ignition coil is ok compression was checked. I checked the fuel injectors and swapped them around with 2 that i knew where working. Check distributor cap and rotor button. Also pulled of the valve cover and checked them everything is in working order but i am still idling rough and is bucks when going uphill. Codes were originally P0303 P0301 P0304 and a random/mutiple cylinder misfire code. Can anyone help I am out of answers... lol