What does each component of the exhaust do?

DarkJak

High Flow Cat-Our stock catalytic converts may be the most restrictive part of our exhaust. It processes the impurities of exhaust gas into cleaner gasses, so it doesn't smell bad and hurt the environment as much. HFC's will increase the flow, increasing volume and often cause some rasp because of the additional flow.

Test Pipes-They'll eliminate the cats completely, so foul gasses aren't converted, causes exhaust fumes to smell bad. BUT they are less restrictive than HFCs and as a result, will be louder and raspier in most cases.

Mid Pipes-I don't see too much variance between mid pipes in cbe's, but many have resonators to reduce volume/drone in the cabin

Axle Back-Usually this section of the exhaust has the largest muffler/resonator parts and will change the tone more than other sections

Headers-Switching to long tube headers will help flow much more vs our stock headers (louder). The stillen short headers still increase flow, but not as much. Seems like LTH's will increase pitch too.

Aftermarket headers and cats are all lighter than our stock systems. Most CBE's will save weight too due to smaller muffler/resonators and more straightforward efficient design. The largest exception to this that I know of is the StillenCBE, which is ~10lb heavier.

You can find some before/after videos of people who installed individual parts on youtube too.