I have a raypak p-r406a-en-c (natural gas) unit and I'm having a flame rollout problem. I looked at the flue and it's clear. There's no obvious issues (no dead beasties). No obvious damage. I tried adjusting the pressure a bit, 3/4 of a turn counter clockwise didn't change the flame height. It's pretty much tightened clockwise in it's original state. Since I saw no change, I stopped playing with it and put it back where it was. Are there any other customer capable items that I can do before bringing in the professional?