Answers to your questions:
Aquamist does not seal the box. If it is sealed, be careful.
1) The purple wire goes the +12V side of of the head lamp. If you ground the purple wire the gauge will go full brightness.
2) The user cable (green harness) is important if you have a "direct injection" engine.
3) The ECU cable (grey harness). the red must be wired to a switched 12V, only active in the "pre-crank" key position. The blue wire goes to the "signal wire" of the on-board MAP sensor if you have one (I don't have a pin-out diagram of your ECU, if you can get one, I will make a specific wiring diagram for your car). There is a guy called Softic on this forum, you might like to ask him to help you a bit, ask nicely. Don't use the word "WTF" if possible.
Here is one post he started:
http://www.aquamist.co.uk/vbulletin/...ead.php?t=2309
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