I need education on the Thermoquad "staged accelerator pump" , that gives an additional shot when the secondaries open

For sure my 9077S base has no vacuum advance port. But the upper part of the carb was by far the best I have, so I swapped bases with another carb and all was well. I just started driving my restored '68 FB FS 340 and got 16.67 MPH the first tank. This was not ideal driving as I was in traffic and working on the carb a lot. So hopefully the next tank will be a more accurate representation of the fuel economy. But i must say, so far, the TQ is a wonderful carb. Just 1 quarter stab of the throttle and the engine starts right up from cold and idles at 1200 smoothly. Can't ask for more than that.