does 4th generation maxima have exhaust manifold(so called header)?

 

All cars have an exhaust manifold (or 2).

A header is a specially tuned manifold designed with high performance in mind. Most OEM manifolds are made of cast iron so they can carry as much heat as possible to the cats. They are also designed to be cheap and to take up as little space as possible. Headers are usually steel tubing that is designed for good flow. These also weight less than cast iron. Wrapping a header with header wrap will carry away just as much heat as a stock cast iron manifold.

 

and to further answer your question..... I have yet to find an aftermarket set of headers for the 4th generation Maxima.