1999 Mitsubishi Eclipse engine idles lower than normal soun

Engine Performance problem
1999 Mitsubishi Eclipse 4 cyl Front Wheel Drive Manual 236k miles

this just happen about a week and a half ago! The car just started to drive weird lower rpm response, hesitation, throaty WRX subaru sound, sorry that the best way I can describe it. Then I changed the spark plugs wires, and changed the ignition coil about 2 years age but I also noticed oil in and around two of the spark plugs to the mid right of the block but no oil was visible anywhere on or around valve cover of the engine. Started the car and still that sound and thumpy type of idling was noticed again it did sound normal at first start but then went back to being horrible again. My cousin said it had to be my catalytic converter and o2 sensors but I only changed the cat out with a new one, then the idling got worse gas started going down rapidly even at idle Now my car is not drivable at the moment, My best guest would be to get a obd2 data scanner and see what codes come up but those run anywhere from 150 200 bucks any way you guys can point me in the right direction, My car has never had this bad of a engine problem ever since a bought in new in 1999 that's why I'm so confused.