Thanks. At least I know that if I have to use the spare, I won't go down in flames like a Zeppelin hit by incendiary fire.Ed:
1: Yes you can use 9-5 spare in your 9-3.
2: You need to change CA to EU in BCM, REC, UEC and maybe ICM and after that you can change lights to alt 2.
3: You can use, but you miss a bit of power (you can not notice this in normal cruising). Trionic will adapt in lower octane.