loud popping from the exhaust? Old gas?

[84 400]

Well the 84 is running like dog.. well you know what. It idles okay but every few revolutions I hear a popping cumming out the exhaust. Truck has sat since 06-07 but has been fired evey once in a while and never ran like this. I did add stabil to the gas before storage. But I think it expires after 2 years. Does this sound like an old gas problem??

If it is old gas what can I do to remedy it? I have heard of "drygas" and other such products would they help??

Thanks for any input... next time I drain the tanks..............