Check all your fuel lines are tightened properly, if shes drawing in air from a loose clip that can cause fuel starvation, I do remember your dad having a problem with the fuel pump many moons ago and if the seals or diaghram is leaking that will cause the fuel to drain back to the tank and likely cause an airlock, it could also be a fuel vapour lock where the engine runs fine until its switched of or stalls and then it vapourlocks and will not restart until the engine cools down which is usually around 20-30 mins.
It could be the paint inside the tank flaking off and blocking the fuel line but I would check the other stuff first.
Another thought, has it got an electric fan fitted, if so use it to keep the engine cool especially in traffic when vapourisation is likely to occur.
Give me a bell Aus if you need to.