paul, i do have a hole in the firewall, with what i have it flys very strong, just not getting the high rpm like some are, maybe it will come with break in and a new prop.
how ever i am having a problem with engine stumble , fly level and pull hard up to do a wall or go into a hover engine stumbles real hard, just on the up not the down? what do you think?
presure inside the cowl over the vent hole in the diaphragm cover is all i can think of, i flew it sat after going through the fuel system with all new fuel lines, running a filter walbro clunk.

xracer