Play with the orifice sizing just a bit. The diaphragm control may be a bit too aggressive with a .060 orifice. Making it somewhere between 065 and 070 may improve the power. The 5920 can be pretty aggressive and if the orifice is too small it can keep the fuel mixtures from richening up adequately during acceleration.
Understanding a balance screw! The balance screw is a gate inside the vapour passage that dampens the normal engine pulses of the air flowing into the engine. Air enters an engine is pulses due to the intake valves opening and closing. The pulses are shorter on a V8 and longer on 6 and 4 cylinder engines. The front diaphragm od the Vialle reg is free floating. No springs. It moves according to internal pressures or vacuum. This regulaor is designed to work with all engine sizes, however the intake pulses can cause the diaphragm to fluctuate to strongly. Closing the BALANCE SCREW dampens the pulsing to the sensitive diaphragm. Too far closed can affect power or even create a hesitation. Don't be afraid to play with this setting by opening it a turn or two and see if power increases.
Lastly, cold start. When you get in the vehicle turn the key on and listen for the solenoids to open. Wait until they shut off. Two seconds. Cycle the key off and on again. Wait 2 seconds and start. Extend this by another cycle the next morning to see if the starting improves. It should if the priming function is working properly.