Is it strictly necessary to jump harness when setting ignition timing!? I mean i friend of mines did his without jumping and works fine Any input is greatly app.

 

Yes, you must jump the SCS connector because the PCM is always dynamically controlling the timing based off of whatever the base timing is, therefor you would be setting timing that is 16 degrees plus whatever timing advance the PCM commands, (the PCM will NEVER retard timing less than your base timing.)