Bosch or Denso are fine to use as replacement of OEM O2 sensors
Have used both without issue over the years.
Upstream O2 sensors(close to engine) are used by computer to determine if air/fuel mix is too lean or too rich
Downstream O2 sensor(s) are used to test if Cat converter is working, they don't effect performance
You only need to replace upstream sensors unless you have a specific DTC code(check engine light on) regarding downstream sensor, downstream sensor(s) last twice as long since they only see "cleaned" exhaust after the Cat
Last edited by RonD; 09-30-2014 at 10:34 AM.