Agree a leak is more likely.... ...but in case it ever helps, a fairly simple test for a Lambda just needs a cheap
DVM. Track down the signal wires, dab the DVM across them then run the engine (leave the probe properly connected to the car). Once it's warmed up for a few moments, you should see around 1v to 4v on it. Blip the throttle, as long as the voltage reading swings quickly then ...