Hey Kirin, make sure with the fuel tank you give the exterior a good clean - my tank wasnt a leaker but when I media blasted it I did find perferations near the exit of the tank (bottom) Good thing or I would have been chasing a phantom.
Also when I gas-freed it (interior clean) I used a product called citra-clean, it's enviromentally friendly and non toxic. I can hook you up with some if you need.