CAN wiring is meant to be twisted with a 120ohm resistor at both ends of the bus. The ECU has one built in for the ECU end so you only need to add one at the far end. However - as I said earlier I doubt this is your problem, it can slow down comms and become more of an issue with a more loaded bus with lots of data on it but a single lambda is not sending much data.
Are you definitely sure that sensor is still getting hot with just ign on, engine not running?
