a hole saw install bit is 2 1/4 standard
the drill bit used for the exhaust is too small for a 12mm wrench to fit over it,
but a 13mm wrench will
the purpose of taping a socket around it is to keep the bit centered in the bore.
those holes are OUTSIDE the air filter. go look at the PBucket page to see , lmk if you need more pics, the filter is only around the TB