Drewpy now you have me thinking. I think I'm going to have to use aluminum for the vacuum lines or there will be a galvanic reaction between the aluminum and the copper/brass. They are highly reactive. Glad you said something I hadn't considered it. Aluminum will be fine in that application.
Shaun
I think Mikuni et al, would have used Alu if it caused probelms, the reason they use brass is that it must be more stable near heat applications