Tip: Try fitting a coolant temperature switch first. Common fault on Vec B and Astra F. Coolant temp sender was dodgy, giving false indication of engine operating temp, ECU adjusts the fueling accordingly and subsequently the engine runs rich sending the emissions up. It may not be that, but they're a damn sight cheaper than charging like a bull at a gate to the Lambda sensor, and in my experience, it is FAR FAR more likely to be that. Good luck
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