About a year ago got code for throttle body and thoroughly cleaned it and codes cleared. Now I have a misfire/chug/jerk under low speed acceleration, steep incline, or under heavily loaded vehicle. NO codes show up. I have replaced plugs with iridium plugs then replaced every ignition coil one at a time, then replaced plugs again. I re-cleaned the throttle body and cleaned the mass air flow sensor. I even had the automatic transmission flushed. I've found No vacuum leaks. I can't spot any bad connectors. running out of guesses. Any ideas or way to find problem? I have OBD II but unsure of factory settings for comparison.