2. Using a 13mm socket, remove the heat shield that is above the exhaust manifold. It is held in place with two 13mm bolts. The Cooper does not have this shield. Once it is off the head, it can remain in that area - you don't have to take it out of the car.

3. Remove the bolts from the cat to the rear of the exhaust system. These are either studs (factory) or a bolt and nut, in which case you will need a wrench and socket.

4. Remove the O2 sensors with the 22mm wrench. There is one after the cat, and one before the pre-cat. Both are best accessed from underneath the car.

5. Remove the exhaust manifold from the cylinder head by removing the bolts with a 10mm socket. The manifold will then drop down.

6. In order to remove the manifold, you will need to remove one of the heat shield panels on the driver side. It is held in place with two 10mm spinners and two 8mm bolts. This will give you enough room to clear the front swaybar when you try to pull the exhaust out.

7. Fish the new header in the same way the old one came out. Install the 10mm bolts (make sure you have the gasket in place) into the head.

8. Reinstall the heat shield underneath the car on the driver side.

9. Connect the header to the exhaust system.

10. Reconnect the two O2 sensors.

11. Reattach the heat shield over the header.