Prepare the o2 sensor for removal with penetrating oil.
Using an crescent wrench or an o2 sensor socket, remove the o2 sensor from the catalytic converter.
Optional: Tuck the o2 sensor up on the heat shield so that it does not get in the way of the removal of the factory exhaust manifold and catalytic converter.
Remove the two 14mm bolts that hold the sub-frame harness to the steering rack.
Lift the bracket away from the steering rack and push towards the engine and tuck it out of the way. This will aid in the removal of the factory exhaust manifold.
Remove the three 14mm bolts and two 14mm nuts from the factory exhaust manifold mounting points.
The exhaust manifold will rest on the upper studs once the all of the bolts/ nuts have been removed.
Remove the two 12mm bolts that attach the oil filter heat shield to the engine. The removal of this piece will aid with the removal of the factory exhaust manifold and installation of the new header.
The re-installation of the heat shield is optional.