After I did some porting to the housing inlet, it was time to start on the wastgate hole.

I smeared some aluminum antiseize on the flapper valve to give me an indicator of where I had room to open up the hole without going too large for the flapper valve to be able to close and seal.

I sat the wastegate housing down on the turbine housing; closed the flapper a few times to get a good 'print'; lifted the WH back off; and looked at the footprint of the flapper valve.

When I saw that the flapper was not able to sit flat and give a nice round 'print', I finally heard the alarm bells. I had a warped turbine housing; not just a cracked one.

Now I had to find out how bad; and why.