I had the same problem.I had to make a bit to get a hole in it.I took a small drill bit and cut it short and JB welded it into a small socket that would still fit my 3/8 air rachet[had to use rachet as a drill because all the 90 degree air drills were to wide to fit back in there].Then I used the short style MAC easy out and it came right out.It was a pain but I am glad I got rid of the leak.

 

when I put the 4.8 back in . . . I broke the back header bolt, and I tried drilling it out. I got a nice deep hole, tapped in the reverse tap . . . and SNAP! . . . so the broken tap is still in there,. . . I can't hear any leaks