I just went through this with my ‘99 Prosport. Sloshed a cup of MEK ( dissolves many tank liners) around for 1/2 hour with a lightweight piece of chain, sucked out 95% of the MEK/liner syrup, let the remaining varnish-like coating dry thoroughly, done! You must plug all openings, protect the paint ( I used saran wrap and masking tape).
Some experts who work in the gasahol industry say its not the ethanol causing tank and fuel line damage, but the benzene, etc, added to increase octane. They insist that ethanol actually absorbs tank H2O condensation so it can be burned, and not sink to the tank bottom and cause rust. Acts like ethanol “gas line antifreeze”.