I flew it again before getting a chance to buy a new glowplug. I tuned the engine and it seemed fine and I had one flight that went fine except about 7 or 8 minutes in I did a loop and the rpms went way down and then it came back up. In the next flight, I was about 7 or 8 minutes in again and the engine died. It seems that it has the problems when it is later in the flight like this. I would normally think it was a problem with the weight in the fuel tank but it has happened on two different tanks like I said earlier.