The throttle position sensor tells the PCM where the throttle plates are, it uses that value (plus a few others) to determine what the desired power from the engine is, it then makes adjustments to the ignition timing (by way of when the coil is energized) as well as fuel timing. Unplugging this sensor will cause the engine to go into a sort of limp mode, where fuel injection is reduced and ignition is retarded. Unplugging this solves the symptom of the problem by changing the way the engine is operating. You will have very poor performance with the TPS unplugged as well as decreased fuel economy.
When you say none of the above, did you test any of it? Or because unplugging something fixed the symptom you decided that testing what was suggested is no longer needed because the 'problem' is gone.
I guarantee you that the TPS is just fine if there are no codes for it. The problem is with something else.
Backfiring occurs when large amounts of unburnt fuel suddenly ignite while both intake and exhaust valves are open. This causes a sudden explosion of fuel and air that travels both down the exhaust and back through the intake. This can be caused by a few things, poor or no spark, delayed spark, valve timing/cam issues, excessive fuel or lack of air. Cam/valve issues are rare in stock engines. Too much fuel has other noticeable symptoms. Lack of air is a possibility and can be tested by checking the air filter or just removing it. Poor spark is the most common, even ahead of poor airflow. Spark can be tested with an inline spark tester, the color of the spark in the tester indicates the 'health' of the spark. Another method to test is to measure the coil with a multimeter, and visually inspect the wires/ distributor cap and rotor. If there was a control system problem, it would throw a code 85% of the time, there are few control system problems that won't throw a code.
