Before I begin, this is NOT a slam on the motor, just a heads up in an effort to help someone else and prevent a problem. My DL-111 has over 15 gallons of fuel and is working like a champ. I am very pleased with all aspects of the motor. During a flying session last week the motor started to surge at high throttle. High throttle ONLY. In short, we found the four bolts that hold the intake manafold were loose by 1/4 turn. After applying locktight and reinstalling, the problem was solved. So, be aware. There is no locktight applied during assembly. I hope this prevents someone else from having the same problem.