ORIGINAL: futaba_pilot45

hello dave.... well here's the deal.... went and got a new manifold gasket (other one was really torn) and ran the engine.... it would maintain a steady run (for once) but wasn't running on the pipe.. i wanted to see if maybe there wasnt enough pressure comming from the tunnel so i cupped my hands around the exaust and pretende i was a adjustible tail cone... it seemed the more i brought the rear section down the more rev's i was geting but i noticed the air was backing up and basically unloading the fan... (causing the higher rpm...) so my question is this... does this indicate that its not getting enough air in? out? or should i check the pipe length? (engines pipe) i have the video of the OK models DJ-1 and DJ-3 and they are haulin some serious butt... the DJ-1 is basically a all balsa zaggi with a nose pod for fuel/ radio gear... and the plane leaps of the ground in about 3 feet... and its engine is exposed and no ducting...