Can't pull out the vacuum nipple from Roush/VMP S.C

[demas]

Hey guys!
I am trying to pull out the vacuum stopper/plug/cork from my VMP (same in the Roush) S.C. in order to install boost gauge. see attached image.

The screwing on this plug is totally messed up and it closed REALLY hard.
Do you have any suggestions on how i can pull this off?
BTW- Can't use the Allen Wrench, it keeps slipping.

This image is the stopper i'm trying to pull but it's not mine, it's just to explain:

 

[5lho]

Go to local bulk store, buy a bag of alum, build a little cup around the bolt out of pop tin or similar, seal with silicone, add water and alum. Leave for 36 hours and the steel bolt will be gone when you get back to it. If you shoot some heat on it, it'll work faster.