Car is miss firing also running very rough by the way it sat for almost 3 months

FIRING ORDER DIAGRAM 1998 OLDS EIGHTY EIGHT WITH 3 8L

click on link...sounds like sparkplug wire is misplaced

replace the injector in no 2 cylinder

Do a Cylinder leak Down Test

You may have bad Valves

Always start with a cylinder contribution test,then
cyl leak down,to check mechanical integrety,before
you start throwing parts at other things

Check for plug leads touching each other. Check for moisture in distributor cap if you have one. Check plugs and replace if necesary

everything unnecessary as the problem is the injectors /fuel pressure or injector wiring
run the fault codes first and save money

the engine miss fire can cause the other codes to set. you need to repair the miss fire and clear all codes after the miss is repaired then see if the 02 sensor codes return. the miss fire is probably a bad spark plug wire a good tune-up should take care of it ........HAVE A GREAT DAY

Look into having your ignition coils tested.

Recheck the firing order; 1-6-5-4-3-2

On the distributor passenger side radiator to fire wall. 2-4-6-coil
On the distributor drivers side radiator to fire wall. 3-1-5

Cylinder passenger side radiator to fire wall. 2-4-6
Cylinder drivers side radiator to fire wall. 1-3-5

Good luck and also check the distributor cap again for proper seating.

you need a new fuel pump

could be a wire crossed, or it's out of time. since you used motorcraft plugs, did you set them properly to the correct gap? replacing plugs without gapping them can cause the sluggishness, out of time can cause the mis-fires and rough running.