Hi, so I recently purchased a 96 cobra with a cat delete already installed. Within a week I got a check engine light and pulled codes PO171/PO174 (system too lean bank 1 and 2) And PO300 (random/multiple misfire). I can definitely tell the car is misfiring but not too bad, so I bought some spark plugs. I read a little bit on my problem and It seems it could possibly be an o2 sensor?? I know theres 2 before the cats and im not sure if theres a mil eliminator installed. I just would like insight on what I should check/replace to fix those codes if it isnt spark plugs.