Searched but didn't find anything. What are the differences between these?

Also... for flanges on BOV's you use aluminum when welding to aluminum, and steel to steel correct?

 

Well you are right about the BOV flanges.

A threaded wastegate flange simply has bolt holes that are threaded. The standard ones just have straight thru bolt holes. Which one you need really depends on your manifold. For example, if the waste flange on your manifold is threaded, then you don't need a threaded wastegate flange. If it isn't, then you need a threaded wastegate flange. Make sense?

 

Ah... so just as long as you have something to bolt it into. Makes a hell of a lot more sense. I thought the wastegate port was threaded or thru.

Thanks.