my 88 xj is sputtering through all different rpm ranges and i cant seem to figure out why. i have replaced the fuel filter and pressure regulator ( no way to check pressure on the rail atm ), i put new plugs and wires in it about 2 months ago, along with cap and rotor. i did notice that cylinders 1-3 have carbon deposits and 4-6 are slightly glazed looking. i haven't much clue where to go from here, and any advice would be appreciated. thank you