Vented gas log makes roaring sound like gas rushing

I have a vented gas log for 2 years with no problem. But this year, it start making roaring sound after it been lighted for about 15-20 minutes. It sounds like the gas rushing and it lasts for 15-20 seconds or so; than it stops for a 10 or so minutes and starts up again for 15 20 second. I opened the vent/damper all the way but it still make the roaring sound. Other than the sound, everything seem to work. Any suggestions will be appricated.
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gunggung wrote:

Regulator? Tony
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