1989 GTE skip and code 25 trouble shooting

[professorbob]

Could a exhaust header flange leak, cause enough heat soak to cause the 02 sensor to cause the ECU to cause the engine to miss fire or starve the injectors. Or could this also cause the code25 to pop up after long driving or hard engine driving?

 

[Nick M]

An exhaust leak before the sensor can and does cause a false lean signal.