Another method with the boost gauge is to do the AIH delete mod and buy a AIH delete plug with 1/4" NPT port. A barb fitting can then we screwed into the AIH delete plug to run the boost gauge.
You can then just put a brass barb joiner back into your stock line - which I presume is the one going to the waste-gate controller.

If you're going to do the EBPV delete you can get the 'high-flow' turbo outlet to replace the EBPV outlet & thereby get rid of the PO's thermacouple hole.

On the good side, at least the PO's PO was monitoring EGT & so your turbo is probably in better knick now for their care.