You will need
New Lambda Sensor
Ramp/Pit/Some other way of getting under the car.
If you've been finding that your car seems to not pick up quite as fast as usual it may be that your lambda sensor is dead.
The first thing to do is to Reset the ECU to check it's not simply an engine management 'thing'. If it's not this then it may be the lambda.
But how do you check? Take your car to a garage and get them to check your readings. Idle emisions shouldnt be the same as revving emisions and if they are in any way, then your engine's not sensing what's going on properly.
To remove the sensor you need to get underneath the car. Follow the exhaust system to the CAT. Stuck into the CAT is a temp guage but dont confuse this with the lambda. Look forward towards the engine from the CAT and you should see another plug in the system. This is the lambda. Unscrew it from the exhaust and then follow the cable up to a rubber gromet. This pulls out and allows more cable to drop out of the car. Pull it gently till you come to a multi-plug. Disconnect this and remove the sensor.
You can find out if the sensor is passing a current with a circuit tester or if you're not sure then ask at a garage to check it. If it's broken then you have to replace it. If it's working fine.... then you have some other problem!