egr or timing backfire

I am thankful for the time and effort you put in your message, for now this is on hold whilel I scrape together cash to buy a car, I really do appreciate your time I had planned to juggle both,
but based on what you've told me I'm look at a lot more serious issues than I can effectively deal with as I cant keep it running long enough to tell if the If the pop is repetitious, as in EVERY time that cylinder fires, because as soon as I put it in gear it back fires an dies