I thought a down pipe and header were basically the same thing. But why would they be called 2 different things. please help.

 

Header is for N/A. Downpipe is for Turbo engines.

 

,Although there is normally a down pipe for a TII engine. there is one for an N/a also. the N/A down pipe goes from the N/A Stock manifold and it eliminates the precats..The Stock manifold is like 30 pounds of Cast metal.
a Header is Basically a piped Manifold and the Pipes leading down towards the cat.The header is lighter and allows more exhaust flow.