Using the engine wiring loom complete from a 1990 e32 735 is my choice for a 1.3 conversion. Everything from intake manifold to neg battery ground was removed complete from a donor car taking time not to cut any wires. A lot of time with a wiring diagram online identified every wire before I started installation. I took everything complete from positive cable to negative cable and everything inbetween. Considerations of installing harness is running all wiring down wiring loom tray above injectors hidden by a nice trim panel so there is minimal exposed wiring for a clean appearance. I drilled a 2 inch hole with a hole saw just below the pass side water drain taking into consideration the ac lines on the interior of the cabin and the close tolerances of the glovebox. The e32 bulkhead rubber grommet fits this hole nicely. I cut the wires after marking both sides with wire marker tape available at home depot to allow the diagnostic connector to be mounted on a custom bracket with the ignition coil on the wsw bottle bracket on the firewall. I soldered all wiring back together as it came out of the e32. After I get it running correctly I will come back and remove all the excess wiring and rerun the wiring nicely and cut out the excess one at a time to eliminate compound errors. I will be using selfvucanizing silicone tape from home depot and other suppliers to wrap the wiring harness when I am completely sure there are no more alterations. The decision to mount the motronic computer in the glovebox was decided by the length of the crank sensor wiring. These are shielded low voltage signal wires with a hall effect signal that is very low voltage. If you cut or damage the shielding on these wires the signal may become compromised and the car will quit running with your grandma in the car. I built a custom bracket above the glovebox after some measuring that attaches to the glovebox latch mounting bolts. Be careful with the length of these bolts or you will damage your dash. I used velcro to attach the computer to the support brackets for easy repositioning. I will probably ziptie for safety over speed bumps.