Currently suggest just to leave the O2 sensor plugged in. The Hyosung GT 650R uses a narrowband O2 sensor as a means to keep the bike EPA legal during light engine loads. Your bikes fueling will become very erratic and inconsistent without the O2 sensor in the loop. With the O2 sensor in place the fuel mapping becomes stable. Because of the small range that Hyosung utilizes the O2 sensor, the EJK does not need to bypass the O2 system and is able to make adjustments to your fueling without the ECU trying to pull fuel out again.
The GREEN zone engages at 1500 rpm with a GREEN/BLUE setting of 4.