NC O2 sensor wiring extension length

  1. My model of MX-5 is: NC2
  2. I’m based near: South Wales
  3. I’m looking for technical help or recommendations on: Length required for NC/MK3 primary O2 sensor extension when fitting 4-1 manifold.

I am in the process of making up a primary O2 sensor extension and would like to know what length I will need. I don’t want to leave this task until removing the manifold and want to have this extension harness tested and ready before starting the job. Do you know what length is required?

Did you make the extension in the end?