I had to put a helicoil in for the aft-most exhaust stud (see the picture). I was pretty careful not to drill too deep. After I drilled, I blew some air into the hole and noticed air and aluminum chips coming out of the hole indicated in the picture. The air was obviously traveling through the channel where EGR gasses flow.

1) Did I cause this by drilling too deeply?
2) Or, does this hole already get into the EGR channel?
3) Is it a problem in any case, or will it be sealed by the stud?

 

If you place a stud into this hole you drilled, what about then? what would happen if you blow air through it?

 

I checked the other holes at the same level and it seems they all go through to that channel. So apparently, the stud seals them. Sure hope so.