You will want to get a drill bit that is the approximate diameter of the sensor. Only the part the sticks into the pipe.
Drill a pilot hole, the increase size up to the size you need, If you have a chrome pipe, go slow, you will burn the tip.
then on the OEM pipe, remove the sensor, cutting a little more material of the pipe to create a flange. I say @ 1/2" 13mm but a little more is one too. Before installing it into the pipe, coat the flange in a MAF safe silicone, most are these days. Push into the holes and tape it down. Let it dry. Then after it dries, peel the tape off, and run a bead around the outside seam. pressing it in with your finger. You can mask the pipe of to have a clean peeled line if you want, just pull the tape off before it dries.