Ok, let me clear this up. No matter what year you have, no one here has headers from the factory. They may be tubular in design, but they do not have collectors and the front exhaust manifold collects into the rear first and then to the cat. This is not a real headers. Plus the front and rear exhaust manifolds are logs. A real header is going to have each pipe seperate into a collector and the front and rear connect to the downpipe seperately allowing for as much exhaust gas to pass through as possible.
We need to move away from people thinking that the older exhaust manifolds are headers. Let me say this one more time, none of the factory exhaust manifolds are HEADERS. They are tubular, but their design is limited to only so much. That'* why when you do real headers on these cars, the */C engines gain 20 HP and 20 lb/ft to the WHEELS. Big difference between factory exhaust manifolds and true headers.
Sorry, just tired of the term "factory header" being tossed around. Not a header folks, just a tubular exhaust manifold.
ADTR 1999 Black Bonneville SE
2003.5 Yellow Mazdaspeed Protege
2003 Azure Blue Mach 1 Mustang