1. pit stop flame outs are usually the result of loading up too much fuel
2. your idea of replacing the fuel tank is a good one
3. make sure your pit man does not overfill the tank, and have him push the fuel tank lid down so it seals, after he refuels you
4. you said you already tried leaning out the bottom, now, does it run well on idle? By that I mean, can you sit and idle for 20 seconds, or does it flame out once you hit the throttle after some idling? if so you are probalby still too rich on bottom (and maybe idle gap too large), keep in mind that small adjustments can help a whole lot.