Mine was a b***h to remove and ended up rounding out.
Soaked it good with penetrating oil let it sit a day and it came out the next day after tapping in the next larger size allen key 7mm. May not work all the time but did for me. Got a plug from a friend who had an old unit lying around and installed it with anti sieze, never had a problem since.
05 F250 CCSB 4X4, 05 VW TDI
4"Banks Turbo Back, ARP Studs & OEM Gaskets,
Coolant Filter, Blue spring, Zoodad
Bypass Oil Filter, Kitty By By, Standpipes dummy plugs
BPD oil cooler, EGR Delete, CCV Mod, BPD Oil Cooler, SCT SF3