What does the pipe that runs from the muffler to the fuel tank do?
 

I've recently built and run in a Kyosho Landmax2. I changed the glow plug after run in and went through the tuning sequence but still had occasional stalls when I open the throttle for a prolonged run. I've played around with lean and rich settings but still had the problem at random times. I then got desperate and removed the pipe between the muffler and the fuel tank and I don't appear to have the problem What's going on, I thought this was to supply positive pressure into the tank?

pressurizes the tank so the fuel is forced to the carb. it basically acts like a fuel pump in a full size car...