Also in the sake of full disclosure this is not a Miata, It’s an old 911 turbo. I can’t get any solid technical input from those forums. They’re not DIY thinking types. Mostly stuffed suits with stock cars.

Here’s a pic of the layout and why I am so reluctant to change things. Drain locations are tricky and any changes in height could jeopardize that. You can see the cut down turbine housings here too.

Its really clear now why it got so bad. The way it looks to be set up you probably have water standing in them almost all the time.

Just heard back from my machinist. He does not believe it’s the studs melting. He thinks it’s just rust from condensation when it sits. Gonna roll the dice and slap it back together with new cast housings.

I don’t know how that could be. I live in a low humidity area. It gets run up to temp on most trips. I do let it idle when I get home to cool off the turbos. I don’t see how it could be that.