Fuel is new cool power 15% pink stuff - I did try fuel from a friends gallon and no difference - I have the engine mounted on a profile so tank on the left side with engine mounted sideways on right side - no pump system in use - Originally thought issue was because I was getting bubbles in the fuel from vibration took care of that added another layer of foam behind the tank and loosened the grab on it - by the way prop is an APC fun fly prop 12.25 x 3.75