anyone hear or experiance this before,i have a spe 26cc engine which runs fine on the stand and also when in the plane on the ground,leans out nice and can get to 7200rpm with a 3-blade 16x8 with a idle down to 1850-2000,as soon as you get to speed after liftoff it drops in power and starts to 4stroke like its rich? land the plane and spool it up and it sounds fine? could i need a velocity stack? any help appreciated,i've gotten lucky so far but its only a matter of time before i lose the model,luckily the flaps have saved my butt to this point,btw its installed on a tt bearcat with a auw of 14lbs.tia........john