You can check whether the sensor is working by measuring the voltage output from the sensor. Most will output 0.45v @ Lambda 1. Below Lambda 1 it’ll read >0.45 or above it’ll read <0.45. On idle warmed up it should be near 0.45.
If it’s not working, you won’t notice a massive difference, WOT is open loop anyway so it’ll only effect your idle and cruise fuelling.
The 4efte ones are a very basic single wire sensor, the 4efe is a 4 wire, both however are narrowband.