Exhaust manafold and headers serve the same function they just work a little different. Exhaust manafold take the exhaust out of the heads and rout them to the exhaust. But when the exhaust comes out of the head into the exhaust manafold it crams it in without a direct rout to make the exhaust flow smoothly. Headers take the single exhaust ports on the head and run them into the right direction to make the transfer a little easier. They have short tube headers and long tube headers. The "shortys" are easier to install because they are usaully direct fit. The long tube headers work a little better but usually requires the exhaust on the car to be modified to make room for the extended header.