hey there good buddy. i had the same issues i dont rember what 2 they were but yes you have 2 bad 02 sensors that are stuck on lean. if you run lean for to long you can burn valves but thats a long time. basicaly all you have to do is get the 2 sensors replaced and every thing should be better. i did not do the switch my self but the 2 that went bad on my car were hard to get to so they say but its an easy fix

Mystique 98 ls T-red MTX B&G springs Turbendz y-pipe (running test pipe) Trubendz cat back with flowmaster muffler Costume intake with K&N filter B&M shifter Magstar wires