[aigel]

Okay, here is the nomenclature:

All 911s have headers. They just happened to be covered by metal to make them also 'Heat Exchangers'. The early cars have better headers, because they tried to keep them equal lenght and also have a sane routing, not having to go through a single cat.

The "opposite" of headers are cast iron manifolds, that mostly do not have individual runners. This is something you find on non P cars a lot. Here is a lot of power to be found if you change these manifolds to headers.

As usual, Porsche already found a lot of power for us and it is hard to top off the factory. This may not be true for smog era cars, but it certainly is true for the early cars that had close to equal length tubing and good routing on the exhaust.

George