lawless

i'm putting together my first L motor and i've bought couple of different manuals and have consulted the dealer, but maybe somebody here can help me. On the passanger side head towards the inside back just in front of #8 cylinder there is a hole that is tapped and shoulded, just like on the drivers side head where the cht sensor goes. my question is what goes what goes in that hole? any help would be very much appreciated thank you