I want to apologize. When I read your original post, and say that you said "why don't you try it" I thought you were responding to my post above. Sorry about that.I agree Supradedupra, theoretically this shouldn't happen, but the slight variables we don't know could be the cause of this problem. I don't know every ingredient in the products he used. A simple and easy test, would be to redo the initial mixture and see what happens.
I edited my first post, but he had originally put seafoam in the car. I don't know how much of it was left in the tank, if any, when the other ingredients were added. The white stuff came from somewhere, either the tank or the mixture.
I don't think it's the Sea Foam either. Sea Foam is simply naptha (petroleum ether), water, and isopropyl alcohol (to keep the water emulsified). Xylene is slightly soluble in water (~200 mg/L in the para form), but is very soluble in alcohols. So, again, I don't think it's the Sea Foam.
Out of curiosity, was there any iron oxide inside the gas tank when you dropped it?