Well... was doing the install today and I took the pins out off the connector so that I could squeeze the wiring through some place tight.... DOH!!!
I dropped the connector into the engine bay.

3 wires from the boost sending unit... 4 pins in back of the boost gauge (top middle).
Can anyone please help me out and tell me what color goes to which pin on the boost gauge?
Facing the boost gauge directly from behind... Pins 1, 2, 3, 4 from left to right.
Thanks!

 

I've installed two of their Boost guages, and the connectors were pre-manufactured. When I did have an issue with a sending unit, I contacted their distributor in Florida, and they were very helpful over the phone. One of the guys there had a MINI for a daily driver too.