A catalytic converter (colloquially, "cat" or "catcon") is a device used to reduce the toxicity of emissions from an internal combustion engine.
See Catalytic converter on Wikipedia for further information.
Whilst using a CRP you need to store your CAT. Basically keep it dry such as at the bottom of an airing cupboard in a bag.
Pre-TF MGF's have the same cat as an S1. Weight 4,3Kg
The S2 CAT is different from the S1.