What I'm trying to find out is what is the residue? Gum from evaporated fuel? Corosion product? Decay products from a slowly disolving fuel tank?
I would put that residu in fresh fuel, in a clear container, shake and see if it dissolves.
If it dissolves quickly, it's probably gum from evaporated fuel. If it doesn't dissolve, or doesn't dissolve quickly, it might be something more serious.
And to be honest, if you have a detectable amount of residue in your carbs and the origin is the fuel tank lining, then it is so severe that your fuel tank would have sprung a leak by now. And if your carb bowls are smooth, not pitted, if you clean them, it's probably not corrosion either.
Note that I'm not a fuel or fuel system engineer. Just trying to apply some common sense.