Yea, I would also run the engine with the cowl off before going any farther. Also, how far is the fuel tank from the engine. If it is two far away the engine will not be able to draw fuel well and lean out. You might need to look at a fuel system like the Iron Bay or Cline to correct the distance problem if this is the case. Switching to a uniflow tank setup might negate the need for the regulator system. This setup is outlined in the July 2005 FlyRC Mag.