I checked the plug wires and noticed some cracks in the outer rubber. I had another set, so I replaced them and took the car for a ride. No backfire and ran great. Coincidence or could that have been it?
Yep that will do it. Bad wires will cause a misfire which dumps raw gas into the hot exhaust system and boom, backfire.
The important lesson is that just because the engine is running poorly doesn't mean the fuel injection is bad. There are lots of things that can go wrong.
