lets start by saying that my check engine light is on and its throwing codes for an o2 sensor heater mafunction, cylinder misfires in cylinders 1,2, and 4. i was driving home about 3 days ago and the car started acting funny. it felt like i had lost some power, and it sounds really loud like i have a really bad exhaust leak but theres only a very minor leak from the muffler. it also burns ALOT of oil so a friend of mine was saying that the piston rings are probably bad and i should probably have it rebuilt. i dont know what i should do or how i would fix this. any advice would be greatly appreciated thanks!