I had similar problem when I bought my Gt6 back in 2000. Bits of rust regularly caused the float valve in the carb to stick open and flood. First solution was the in-line filter - worked but filter clogged very quickly needing changing every six months(ish) to prevent fuel starvation. Eventually I bought a fuel tank repair and seal kit from frost (http://www.frost.co.uk/por15-small-car-tank-repair-kit.html). Not cheap but includes cleaner, rust converter and a sealer that coats the tank insides. Worked very well for me, its been in for many years now and still no bits in the filter and I now only change filter every 2 years. You have to do it with the tank out of the car, but well worth spending the effort. Seem to remember key point was to ensure the tank was fully dry of water before attempting to seal. Think I borrowed the wife's hair dryer, but then that cost me a new one! (HSE note, only use hairdryer if sure all fuel removed - eg by use of the cleaner plus water flushing - don't want fuel fumes to go bang)