getting to the stage now that i want to order my megasquirt with IAT sensor kit comes with either alu or mild steel bung and to order the Tial bov Q same again comes with mild steel or alu welding flange.

whats your suggestions for what material to get alu or mild steel.
also any examples of how to mount these onto the intake pipework the IAT sensor bung is flat so cant see how thats going to be welded onto a round pipe.
dont really have a clue about this.

 

just get the bung from whatever your charge piping is made of...

 

Depending on the shape of the IAT bung it is probably small enough that any small gap left after drilling the hole can be filled by the person who is doing your welding.

As for the material, just match it to what you are using for your charge pipes. If you somehow have plastic pipes, you should think about using metal ones.