M50NV swap, Tach used to work, but not now.

[ScHpAnKy]

I think this advice is for a different model? Below is how I have it wired up. This has not changed after the dash was taken out and then put back in.

Didn't read your above post as an eta, thought I saw '87 325i
In that case, you're right about the wiring - those signals pass through the C104