If you can't find the diagnostic connector on the Kouki (late model) then go fishing. It's supposed to be on a clip on the firewall near the wiper motor (LHD cars). But sometimes it falls down and hangs underneath the intake manifold...

The Zenki (early model) cars have a yellow two-prong plug that isn't plugged into anything. It should have a black rubber cap covering the plug when not in use. It hangs in the same spot, on the firewall, near the wiper motor.

Tuning Tip: When the check connector is shorted, you should hear the engine tone change slightly, as it goes into base timing. If the engine idle doesn't change, you have to check your TPS adjustment.