moesrex

And what if it is cut,what will happen?

Dunc

It is basically a rubbber-like disc on the on inside of the wastegate. If it is cut or has a burn hole through it, you will experience boost problems....such as not being able to reach full boost.

I don't know about all wastegates, but on my old deltagate it was very easy to change. Just undo the bolts around the edge and then you'll see that rubber diaphram.