I have a problem that has persisted for several years. Each year, a service guy tries another solution. The heater bangs like crazy, and it's not the ductwork. We have cleaned it, replaced the mother board, checked the gas pressure, checked the voltages, cleaned the flame sensor, and replaced the gas valve, to no avail.
Here is a video I posted online. It's pretty dramatic. Any ideas? http://garmentdeli.com/Furnace_Banging_Noise.wmv