There are advantages of running aftermarket headers. The headers will run cooler, and bring exhaust gas temperatures down. The stock headers run very hot due to their design. The aftermarket headers will allow the STI engine to run much more efficient.

There are advantages of running aftermarket headers. The headers will run cooler, and bring exhaust gas temperatures down. The stock headers run very hot due to their design. The aftermarket headers will allow the STI engine to run much more efficient.

If you look at the stock exhaust manifold, it has a long runner that runs into the second bank of cylinders on the passangers side cylinder head. This collision is what gives the wrx the distinctive sound, but this sound is also the sound of ineficiency.

Other options for more powere are to port match each fitting on the stock header. If you look at the stock header, there are two cast iron pieces that are connected by a steel section which is wrapped with heat shields. The connections between these pieces don't match, and could be improved by gasket port matching each side.

The Gruppe-s equal length header is made well. The joint welds are nicely done. If you compare the stock exhaust and the el header, you will notice that the el header has larger pipes. This causes a loss of low end torque, but with nice payoffs in the mid and uppper range.

Wrapping the el header should help bring back some of the low end. Some people either use thermal wrap, or a header blanket.