I played around with this problem in the past on a stroker motor with a bigger cam.

1) Drilling throttle plates may lead to booster fuel dribble.

2) Cracking open secondaries could be difficult for a number of reasons but mainly because they are so big and it would need to be done almost to perfection.

What I did was take a tee off of the PCV hose and used different orifice sizes, it seemed to work well but I did not mess with it very long. You would want to have this extra orifice take in filtered air. I tried many orifice sizes and dont remeber what I ended up with but it was not small, (I think around 3/16 inch) You would want to use a wideband A/F device to iron out your system.