Just wondered what the proper way to uninstall original ECU and install new ECU as far as battery connection goes. Should negative be removed or positive or both? Or should I change ECU in 5th gear while driving down highway?

Seriously, I don't want to fry anything. Did search but found nothing. Thanks

 

Disconnect the negative battery terminal. That's it.

I guess you could try doing it while driving down the highway in 5th gear, but I wouldn't recommend it.