What makes you think it is actually "rich" at idle?
it is very very rare that anyone needs to mess with the idle air bleeds.
Very small changes +/-.001" make a big difference.
It is very easy to screw it up.
It is very unlikely that anything needs to be drilled at all.
Put the the friggin' drill down.
post complete engine specs/carb sepcs and tune up specs. It is probabily not rich at all.