Exhaust Header for 2004-2010 Chevrolet Chevy Cobalt/Hhr/Saturn 2.2L/ 2.4L I4

Replacing or upgrading your exhaust header is necessary for both engine performance and sound. Whether on or off the track, exhaust headers provide more horsepower and improved exhaust sound. FLASHARK offers many products to help you create your own custom engine headers. It's really easy and convenient to use: direct bolt-on, no modification needed. The 4-1 off-road racing headers are designed to allow the exhaust gasses to flow more freely from each cylinder and combine in a more efficient manner.
Tubing has been optimized for the 2.2L/2.4L engines. 

Specifications:

Brand Name: FLASHARK
Model: EH28053
Certificate: ISO9001:2000
Application: Automobile Exhaust Header
Material: Stainless Steel
Surface: Mirror Polish
Inlet/ Outlet: 1.625" X 0.875" (Oval)/ 3.250"

Exhaust Header VS Manifold, which is the better choice? 

The structural differences between exhaust headers and manifolds are the material and size. From the material, exhaust headers are made of lighter, thinner steel, while exhaust manifolds are made of thick iron. Exhaust headers are also longer than exhaust manifolds. When in use, exhaust manifolds create back pressure, which lowers performance. Because each cylinder of the engine is given its own tube, however, headers eliminate this problem; thus, allowing the gases to exit without the creation of back pressure. Therefore, exhaust headers are a BETTER choice than an exhaust manifold.