Problems after exhaust install and 02 harness

That wire is for your low oil level in your pan, once it goes down a quart that light should come on,i dont understand how the o2 harness can be plugged into some random plug and be working fine before but now that its were is supposed to be its not?

You are correct about the placement of the harness, its plugged in under the mass air and runs around the front of the pan to both banks where the o2s plug in,have you owned the car long? sounds like someone monkeyeed with it and didn't do things correctly, if you are going to keep the car you might want to invest on a INNOVA code reader (part number 3145), they are cheap and beats that counting flashes and beeps scenario.

When resetting the computer disconnect the negative wire and then turn your headlights on or hit the brake pedal a few times, that will drain whatever power is stored in the car, if the car was changed from auto to standard and someone used the wrong harness that could also be cause for other issues, something else to look for.

When you swapped them out to your new off road pipe did you happen to see what they looked like? if they are completely carbonized and covered in soot it could cause some smaller issues but i wouldn't say major stuff like bucking and jumping, o2 sensors help the computer develop the proper fuel ratio for the engine by reading the oxygen present in the exhaust etc and adjusting accordingly so you might have detonation issues but i think your problem is elsewhere.

You mentioned before you did all this work the car was running fine,so it wasn't missing or nothing? i know this is not the right way to do things but have you tried to start it with the o2 sensor wiring disconnected? just for grins? might be worth to see if it changes anything, these cars are really easy to work on but sometimes you get a gremlin and it can make you question your sanity,lol

Sounds good, Yeah sometimes it takes trial and error,i have a 89 and a 91,i have had just about every issue these cars are famous for,lol

Sounds like you have a nice setup, i tell you a story about my 91,many years ago i had this issue were i would drive a few miles and it would die,if i pressed the brake pedal it would either die or the radio would cut out,i was at my wits end and i was throwing parts at it which is not the thing to do,one day on my lunch break at work i was messing with it and i went to start it and this coworker was walking by and he said "man, your car just arced bad by the firewall" it turned out to be the 3 dollar ground strap that goes from the intake to the firewall, after i replaced that i had no more problems with it, the old one was green with corrosion.

Some car brands i have seen dragging ground straps on the ground and they run perfect but these cars we own are not that way,they are very picky about grounds and clean electrical contacts.

Make sure the ECU ground behind the battery is in good shape as well. There is also a ground wire that is part of the injector harness that is typically grounded on the back of the passenger head or bell housing or on the intake. Make sure that one has a good ground as well. Believe this wire is orange?

Yes, like Aerocoupe said,your injector harness should have a orange wire coming out of it around the drivers side towards the back, this wire needs to be grounded, its usually grounded to the last intake bolt or behind around the bellhousing like previously mentioned, in the picture im sending you,see that lone wire around the middle that has the eyelet ? thats the wire you are looking for, needs to be grounded, its not easy to see, look at it from the passenger side, just lean in and you might see it bolted somewhere.