Engine misses sputters-after load

89 xj 4.0 auto. Jeep seems to loose a cylinder and begin missing after long pulls up hills, or after spinning in the mud. I will shut it off and when I restart it seems like I pulled a plug wire off. It clears up If I hold it at half throttle for a minute or two, I have replaced every replaceable sensor and tune-up part on her including two o2 sensors. Even if I'm cruising on the highway at 2k and stop and turn it off,go to restart and same thing sputtering like its missing a wire or two. Any clues?

have you replaced the fuel return cylenoid?