All our Commodores left the factory with a pretty generic, safe tune, so you could get away with running any old fuel and still be okay. Running solely 98 means you can add some timing then play with the VE/VVE tables to get fuelling better dialed in. PE (power enrichment) can be adjusted to come in earlier and target AFR changed to suit. Turning off torque management in the engine is common but leave some in the 6l80 trans tables if you want it to live. Adjust fans, limiters, shift points, shift times, torque tables and your nearly done......nearly