Some speculated that the engine was internally built. The JDm came with portion of an OS Giken drivetrain part attached to the engine. Looking at the dyno charts A/F numbers show it was running quite lean which is still a mystery:
I dont know what the deal was with that engine....It ended up skipping a tooth on the timing belt a few months later...
But it was 91 octane, 15psi, stock automatic turbos and cams.