i was told the best place to get the tank treatment was a motorbike accessory shop,as they carry this sort of stuff.you could always take the tank along to a radiator repair shop & ask if they can steam clean the tank,then treat the tank with the rust treatment.i recently got the fuel tank in my sunny serviced & baffled for $140 at parramatta radiator repairs (shameless free plug),but they're on the wrong side of the world for you.what's even worse is the rust that'll pass straight through 2 filters & clogs up the jets(or in my case the injectors).