Just to clarify the "has it got a 'kat' or not" the twin pipes drop from the manifold into a box beneath the drivers possition (British car, so that's the right hand side guys! ) which twin pipes to the other side of the car at another box before going up and over in a single pipe to the rear box beneath the bumper / boot exiting as twin tail pipes. The first box has a heat shield over it but this has recently become lose and the rattling is driving me mad! That's a 'to do' for a dry day... Are there any characteristics that denote whether it's a cat by looking at it?

I have been pondering taking a learning curve in pipe bending and fabricating a homemade de-cat from ERW or similar steel tubing but that will be when I'm rich again (it's the being a new daddy money vanishing problem, sure most of us here know that feeling). Aside from the environmental (and possibly legal, such as certain US states) is there any need for the cat? Will an o2 sensor work without one? That is to say if I ever constructed the de-cat would I benefit from installing an o2 mount in one of the pipes?

Thanks for your continued input,

Glyn B.

P.S. the weather never held out for installing the sounds