the one out of the 540. as of splicing it into the e30, that is all up to you to find out.
when i was checking out the sti swap for my forester, cobb tuning said it took 3 months for their electrical guy to get the harness wired correctly. and those are guys who deal with these cars daily.
I know a lot about cars. I can look at a car's headlights and tell you exactly which way it's coming