Ok I am running a 73 1.7L F.I. car, that just decided to start backfiring at idle and occasionally under load. When the car backfires under load (intermittent) it seems to miss at the same time. I checked the timing right before i went to hershey last weekend, and it was on. I have also checked for vacum leaks with carb cleaner, no leaks. I also have no exhaust leaks. I thought it was possible that the points are on there way out but have not changed them yet. Any ideas??

sounds like a spark plug or wire breaking down. get a pump spray bottle with water at night and spray (mist) the water on the spark wires, that will show if any of your spark plug wires are breaking down (leaking/shorting). COOL light show