Foz

Back in the day, it used to be that premium unleaded was only $0.20 more than regular unleaded. Now, I've seen premium be up to a dollar more than regular. So I modded my 928 with a fuel selector switch. Basically, just an extra pin to the coding plug with a switch that grounds it to activate 'Australia' mode (87 octane fuel). If I ever want or need to run premium, I just unbutton the carpet covering the EZK/LH and flip the toggle switch. Mine is an '87. For '90-'95, the coding plug is different with a 150 ohm resistor, so please be aware.

The Forgotten On

You can do the same to the LH 2.2 on the 84 (euro) 85 (US) - 86 with the 2 octane loop wires. You just need 2 switches.

1 for the LH and 1 for the EZF.

Foz

I think you could probably just use a DPST (Dual-pole single-throw) switch instead of two separate switches. The switch shown above is a DPST switch (6 contacts).