Backfires while idling after checking compression Options

[ndtman]

I have a 76 2.0 with the stock fuel injection that I am bring back to life. It ran fine, but I decided to check the compression. After doing this, the car now backfires a lot while idling (every 2-5 seconds), and even more so if I dare throttle up. With the dual exhaust mufler, I note that the backfiring is coming from cylinders 1 or 2. I swapped out both plugs and wires on 1 and 2, but the problem remains. All the spark plug wires are routed to the correct cylinder.
I found that if I disconnected the spark plug wire to cylinder 4, the car would not backfire, and ran smoothly. Replacing the #4 plug and wire didn't fix the problem.
I plan to replace all the plugs, wires, distributor cap, etc, but was wondering why my testing is giving such confusing results. Bottom line - the only way I can fix the backfiring at idle is to disconnect the #4 plug wire.
Any ideas? Thanks.

[bulitt]

An exhaust leak will cause a backfire as it introduces air into the exhaust. But you also need some unburned fuel to cause the problem. If your ignition is retarded some fuel may not burn completely in the chamber and then burns in the exhaust. However this would occur with more than one cylinder. Sounds like you may have a bad spark going to cylinder 4 causing unburnt fuel into your exhaust. So pull the number 4 plug and see if it is wet or black. Check the resistance on the wire from one end to the other. Make sure your didn't pull off the connector. Make sure it is fully pushed into the distributor and onto the spark plug. Also as mentioned before make sure you don't have a dirty (carbon) distributor terminal (s). Check your ground also. And you stated you can hear an exhaust leak, which needs fixed.