35 pdsit and throttle plate hole

So I recently got a pair of 35 pdsit's secondhand off here.

Im curious to know why the throttle plates have holes in them. I see a common mod with the 34 PICT is to close off the hole with a rivet or solder to increase the vacuum seen by the progression port, and also the vacuum port when using a SVDA.

Is there any benefit in closing the hole off for this application? I've got a 1640 with SVDA and antipulse valve, the 35 PDSITs, 30 vents, jets: 55 idles, 160 mains, 90 air, balance tube in place, accel pump set at 0.8cc/suirt.

Engine is running ok but it's definitely lacking the crispness I'd expect