I am going to write on something a little different and old school.
4EAT Sport Mode Upgrade.
Note, 99 usdm is comparable to a 98 jdm. Also, 95 usdm to 94 jdm. If you disregard this you will be in the wrong generation, your looking for the…
91-94 Legacys: Move the female pin on the 20 pin connector from postion 6 to position 4. “manual” button on the shifter turns on the “power mode”.
95-98 Legacys: Ground pin 4 on the 20 pin connector to a chassis ground. I’m not sure about the 99’s as they changed some things with the bellhousing pattern.
What I have gathered on 99-00: Ground pin 20, between blue/white, white/red wires on white connector.
Supplies Needed: at least 2.5 ft 18 guage wire, ground, 2 position switch, TCU pin and pigtail.
The JDM power switch is at the back of the gearlever, early 90’s SVX’s came with a power mode button in Japan.
Additionally; modify your TCU.