Waste gate shaft not moving...

[MercFan]

I have an '87 300SDL that I've been working on - had a plugged up exhaust that I recently relieved.

While I had this area of the engine apart I tried testing the waste gate - I applied pressure using Mighty Vac hoping to see movement in the rod that connects to the waste gate. I heard a good pop when I applied pressure but the rod never moves! It seems stuck in place. I tried tapping on it with various instruments trying to get it dislodged but no joy... I suppose the risk form that condition is that the turbo can over-boost the motor....

What do I need to try to get it to move?!