BRZ/FRS/GT86 (2012-18); which tuning ROM?

All ROM versions for these applications are given under Help, Feature & Licence Information and Supported ECUs.

It is vital you ONLY use the ROM that is specified for your region: USA ROM (C and D versions) share the atmospheric pressure sensor with the fuel tank and these sensors are not fitted on European and Japan-region vehicles; using the wrong ROM will give you incorrect atmospheric pressure readings that will give rise to other issues.

Make sure you base your tuning on the latest ROM revision available. Denso are constantly developing, improving and bug-fixing, so why not take advantage of their hard work? Here we can see that the latest EURO region ECU ROM is the A01G (which replaces the 700G, 900G and A00G).

What's so special about the A01* revisions or the latest B00* revisions?

The latest release is the ZA1JA01* and it's the most important update since the release, and not only because it includes a Transient Ignition Retard feature that helps prevent damage of the Direct Injector seals in the combustion chamber. The 01 update allows Transient Ignition Retard to work beyond 5000rpm now, and this is important for race cars.

The Transient Ignition Retard amount has also been calibrated to remove -35deg of ignition timing upon lift-off for a certain cylinder-fill percentage. The map scaling value has also been changed to allow up to -50deg of retard over the previous limit of -30deg.