[Ben006]

Vacuum is a better idea.
The exhaust is vibrating a lot, and electromechnical stuffs don't like that :/

Were to get vacuum from? Easy, there are a million vacuum hoses on our engine! or at least that's what it looks like when I'm working on one... ^^
Just use a T fitting on an existing vacuum line and you're set!

The third fitting is a venting port. If you apply vacuum to something, but then you just close the line, vacuum is still present, and the solenoid is not doing anything. You need a vent to get atmospheric pressure back in.