[Mk2] [Turbo] Speed sensor wiring -sorted

[sir chad]

Hi, my Speedo isn't working, Rev2 Turbo with factory LSD.
I've checked the wiring and I don't have 12v feed to the sensor.
Wire colours are:
Black/yellow
Brown
Purple

I know the brown is ground
I believe the black/yellow should be 12v from ECU/ign which leaves purple as feed to dash.

Q.1 Have I got the wires identified correctly.
Q.2. Where is the best place to splice a new fused feed from (pin on ECU??)

My bgb is for a 91 so no help as the rev1 has a mechanical Speedo.

any help appreciated.
Chad

Update:
All above is correct, spliced into a switched + near ECU and added a fuse for good measure.
Thanks to Paul D for the 93 info.