V8Astro,
I just bought a Wiseco Fuel Controller -- it's also made by Dobeck and I'm sure it's identical to your EJK. On the box mine says, "Optional closed-loop (self tuning) operation with addition of O2 sensor." This would imply that it's OK to leave the O2 sensor connected. The manual itself doesn't make any comment regarding an O2 sensor.
I just bought a Wiseco Fuel Controller -- it's also made by Dobeck and I'm sure it's identical to your EJK. On the box mine says, "Optional closed-loop (self tuning) operation with addition of O2 sensor." This would imply that it's OK to leave the O2 sensor connected. The manual itself doesn't make any comment regarding an O2 sensor.