You may have to find solder points on the logic board that gives the correct voltage to your tracker. It may be 3.3v or 5v. I don’t think you’ll find much info so I recommend looking at schematics (if you know how to read them) or use a multimeter to look for points that will give the correct voltage. Try to use points that are closely related to ac and battery power since I believe those are the best to draw additional current out of. Drawing current from points that lead to other components like the backlight, cpu, etc. may make the board malfunction. I don’t know anything about this on MBPs, I’m speaking from adding 12v led’s and 3.3v/5v glitch boards on Xbox 360s. Which is not the same as you’re trying to do.