Doesn't sound like you let a lot of corrosion build up, which is generally cause of connector problems. Had exactly same issue, even with new EFI harness ! Intermittent dead cylinder (#3). Code 34 then 55, over and over. Thought about, it and figured since ground signal is sent to all 6 in micro time I would test by running jumper ground wire. Bingo ! Idle was perfect. #3 coil pack disconnect affected idle same as other 5. Drove the Z for a few weeks with the splice. Ran fine. Downside over time would be stress placed on ECU driver that sends ground signal to both injectors. In fact, Gary (DVDBURN) currently has ECU for driver repair.
