I believe natural gas pressure is only 6 ounces. I would look at the diameter of the supply pipe. I don;t know what the exact specs are, but I do know volume is important. The longer the pipe from the main the larger it must be. Does your boiler not light when other appliances are in use? I would be concerned about the loud bang. It could be combustion taking place.

Natural gas pressure is usually given in inches of water since the PSI is so low for most equipment it would be hard to measure.

I usually measure it with a bucket of water and a section if tubing.
Connect tube to gas line, submerge end in bucket to bottom, open valve, pull tube out of water until a bubble of gase is just starting to form at the submerged end of the tube.
Pinch tube closed right at the surface of the water and pull it out.
Measure the length that was still submerged.
That is the gas pressure in inches of water.

Either high or low can cause problems.

You need to check the pressure with the equipment operating since the flow will result in a drop in pressure.