fuel tank cleaning

Just removed my fuel tank off 83 GTI, its in need of a major clean as it was left standing for 15 years with fuel in the tank. As a result its left a brown sticky residue. A local radiator specialist are able to soak the tank in acid to remove all the crap. Would anyone know if there is anything in the tank that would be damaged by a soaking in acid? Or are the replacement tanks from GSF as good, I have heard there is no baffling in the pattern tanks

Help

I would try diluting  carburettor cleaner with some petrol and leaving it in the tank for a while, it should dissolve all the gunge.

Yea I'd try swilling some fresh petrol around to see if it dissovles the stuff in there.