i get what you mean, DV valve is a good example. not sure what it is, i assume diverter valve, but its irrelevant to me so i don't really care.
catback system... surely it would be obvious from the rest of the topic? you know what a cat is, right? catalytic converter? on your exhaust? so a cat back system would be an exhaust system, from the catalytic converter back. ie not the cat, down pipe or manifold. i personally don't see this working, logic would expalin most things, if you don't know what the topic is about and cant work it out from the rest of the topic then its either irrelevant to you (or anyone else) or if not, ask!