How old is the Cat converter?
The Cat is there to "burn" any unburnt fuel that remains in the exhaust.
The 1990 2.3l should have a distributorless ignition system, but an EDIS style so a Crank Position Sensor(CKP) but not a Cam Position Sensor(CPS).
CPS was added in 1995 models when sequential EFI was added, I believe.
There will be a separate module that controls the coils firing, not the PCM, this module controls the spark timing.
Your Code 18(check base timing and advance timing) might mean there is a problem in that module.
If you had a CPS then that would be used for spark timing.
The dual coil packs can be overlooked as a problem, since one coil in the pack can fail and not cause a misfire so it goes undetected until emissions are tested.
The engine will run on just one of the coil packs, so you can unplug one coil pack to test if the other is firing on all cylinders, i.e. no missing
On a cold engine I would unplug the intake side coil(spark plug wires go to intake side spark plugs), then start engine, should not be any missing, turn off engine, exhaust coil is good.
Then plug intake coil back in and unplug exhaust side coil, restart engine.
If engine will not start don't panic
Some have reported the exhaust side coil was used as the "starting coil" so intake coil isn't fired on startup, if this happens then move the exhaust coils wire to the intake coil and plug it in there, so now the intake coil can be tested.
Should fire up and not miss, turn off engine, intake side coil is good.
O2 sensors are like spark plugs in that they do wear out from use, 60,000-80,000 miles is the recommended change time on these, but I have 300,000 on my 4.0l engine with factory O2 sensors, so......
The O2 sensor feeds the computer data on how much oxygen is in the exhaust, this helps the computer adjust the injectors to fine tune lean or rich mixtures.
If the O2 sensor starts to wear out the engine can run a little rich and the computer won't know it, the O2 sensor is sending the computer incorrect data.
If the O2 sensor fails completely you will get a trouble code, but no code until then.
The 1990 2.3l should also be using a MAF(mass air flow) sensor, this is on the air intake, it supplies the computer with information on how much air is coming into the engine and at what temperature, this allows the computer to adjust the injectors for the best Fuel/Air mixture.
These get dirty and can cause lean/rich issues, but they can be easily cleaned, read here:
http://www.therangerstation.com/tech_library/CleanMAF.html
Code 96 is about fuel pump power, your Fuel Pump relay could be failing, so is not closing and opening when it should, the computer controls this relay by grounding it.
Code 98 could mean Computer has an issue, or just needs to be reset, unhook negative battery cable for 5 minutes then reconnect it, that will reset computer, or if you have a scan tool then use that to reset computer.
Any time you clean or change sensors you must reset the computer, or it will continue to use old sensor data, reset makes it relearn how each sensor works.
And "new" no longer means "it works", new now means "never tested", so don't automatically assume a new part doesn't need to be tested.
Which is why testing old parts is better than replacing them, new parts can compound a problem as you are just adding more variables.
Welcome Visitor! Please take a few seconds and 
