Worked for me on my test stand....The drone engines we run in the race planes were pushers with the carbs facing straight forward...the carbs are custom castings using Walbro internal parts..There is no pump function or diaphragm, crankcase pressure is used to fill the cavity under the inlet diaphragm...The cover over the diaphragm has a small brass tube going at an angle from the flare at the front of the venturi to the space over the diaphragm...There is no other hole in the cover..Worked fine in the drone...The carbs were vertical in the race plan so the tube was not needed. I put a fitting in the cover and ran a tube through the firewall to the dead air inside the fuse.....Worked great, clocked 234 mph....
One of the other racers tried using ram air but didn't use the tube in the venturi with a fitting in the cover..He never got it to work and I didn't volunteer any information