Looking for someone's ideas on a problem I have. We were flying my son's trainer the other day and when he would get it into a dive and I would take over control and level it back out, the engine would sputter and sometimes quit. I took out the fuel tank and checked the clunk-ok. When on the ground I would point the nose down and then up trying to recreate the problem but it would run fine. I also tried to richen it up a few clicks but that made no difference. The centerline of the tank is slightly lower than needle valve. Any input would be appeciated.