Believe it or not, I've seen this a number of times before. The one time that I could not remove it with means already mentioned here(oil, air press, etc.), I filed serrations in the end of a piece of sched. 40 pcv pipe, drilled opposing holes in opposite end, and inserted a long bolt for use as a "T" handle. With patience and pressure, using the serrated end as a saw, the obstruction will be removed. It took me cutting new serrations a number of times, and I had to deal with removing a small amount of pcv residue, but that was easily dealt with, and no damage to bore. Good Luck.
Okievarmint- Disrupting the Raccoon way of life since 1955