Hey fellas sorry for asking so many questions lately, ive recently pulled my engine and done a manual swap and im almost certain ive installed everything correctly however i have been getting a check engine light usually once the car is warmed up and will start backfiring on deceleration or when i let off throttle only one pop however the volume will vary on 2-5 minute drives its pretty quite backfiring however the longer the drive the louder the single backfire will get on deceleration. I decided to change the Pre Cat o2 sensor as i noticed when i pulled out the old one it was chalky light grey, while i was changing it to a new one i noticed the thread was rusted on the headers but still screws in just spins on the spot once it gets to a certain torque (still too loose for a o2 sensor) so maybe it has a poor seal and is getting bad / false readings causing the engine to run rich? On top of that there has been two occasions of parking the car after a 10 ish minute drive and once returning to the car it will start then die immedietly after 1 second of idle, all i did was wait 5 minutes in the car and it would start up again perfectly fine. i also notice rough idling when started sometimes.
any ideas on potential causes would be appreciated cheers