As Dub states on his website, most of the problems with engines that are returned to him turn out to be tank problems rather than engine problems. In an SAE or AIAA heavy lift competition aircraft, the students FREQUENTLY place the tank as an afterthought. Here at FW Thunderbirds, when we do the inspections for the SAE competition, it is frightening to see what some of the students do. If you are not already using a bubble-less tank (Jett or Tetra) then GET one. Also, check for pin-hole leaks in the tank, tank liner and fuel lines. Make sure that the centerline of the tank is approximately 3/8" above the venturi. While these suggestions may not cure your problem, they will certainly prevent others. Trouble shooting engine problems is always difficult. While it may not apply to the .46, we have to set the Q-40 engines off pretty rich, WAY below peak. They heat up and lean out when airborne. We have also found out that the technique of peaking them out on the ground to full lean and then backing them off, causes the engines to overheat and have erratic runs. It is best to simply run them up from rich to a pre-determined rpm and avoid the pre-heating.