The bottom of the throat (below the throttle plate) needs to
be enlarged with a 1/4 inch drill with a 45 degree angle.

When you say 45 deg, is that half the angle (i.e., it the total included
angle 90 deg)? If so, you can buy "spotting drills" with a 90 deg point
angle.

You know, I'm not sure. The plans just say 45 deg angle, but
I think that really means a 90 deg point. Good suggestion!