Last year I replaced the control board and that solved the problem of no spark to ignite the flame. It did not address the gurgling noise made by the flame. It was not caused by the air/fuel mixture. I ordered a new gas valve from Amazon, installed it and the flame is quiet again. [I know describing a flame as quiet or noisy is not the correct, but it's the best I can do right now]
Installation is easy and I was comfortable doing it.
Turn off the gas
Unclip the DC supply
Unscrew the gas feed line
Unscrew the single screw that holds the valve to the bracket.
Remove the gas valve.
Remove the gas jet with vice grips and put on the new valve.
Put the new valve in place, attach it to the bracket, put the supply line back on and plug the DC supply.
Turn on the gas and wait much longer than you imagine for the gas to get to the WH.
Fire it up.
Turn it off and check for leaks.