[stallion112]

I agree, the slots should be exposed around 0.020 or to form a "square" shaped slot (width ~ length of exposure).

A much easier way to get more air in rather than drilling holes through the butterflies is to crack the secondary butterflies just a tad. It's worked for me on several engines. The set screw is accessed from the bottom of the base plate under the secondary linkage. It acts as a stop for the linkage.

Just a small adjustment ..... a little crack will go a long way.