I have an L20 (4.8L with VVT) with e38 and 6L90E with T43 controller and using veee8's info it works exactly as it should. This engine was out of a van if anyone is curious.
If anyone is looking to make their own harness you'll need:
6L80/90 connector:
Mouser
Cable seal:
EFI Connection
8.25k ohm 1% tolerance resistor:
Digi-key
4.42k ohm 1% tolerance resistor:
Digi-key
1.5k ohm 1% tolerance resistor:
Digi-key
You'll also need either two switches or a momentary on-off-on switch. I recommend the second so that up and down can't be requested at the same time. I know this is from 3 different places, but all the part numbers are here. The kostal connectors for the transmission are hard to find.