Curious? What prop and rpm do you get? I use a 20x6 Pro Zinger and get 8000 with a modified G38 muffler. Test flew mine for the first time Monday evening and was getting some gurgling when at a low speed. I leaned the low needle about a 1/8-1/4 turn and cleared it up. I'm still a little rich on the high side and have close to a gallon of fuel run threw it. Mostly on the ground (just like to hear it run I guess).