Here it is:
Push down all the way on the gas pedal!
My gas pedal travel got a little stiff at the end. I realized the gas pedal wasn't going through it's complete range. Applied a little WD-40 to the cable and linkage and next time out I pushed a little harder on the gas pedal, and what do you know, quite a bit more power when the secondaries pop in. A real seat of the pants difference.