It was my intention when spec'ing out my 2.5 L S14 that the engine be well balanced. All of the various components would complement each other. Since I had committed to going with a ported head and aggressive cams, it was only natural that the intake and exhaust by suitably matched. In the case of the exhaust I felt that larger tubes for the header would be in order. The BMW Motorsport Group A header fits this definition. I purchased the unit from Turner Motorsport. It is actually billed as a Group A "Rally" header and costs a little over $1000.

Looking up the factory p/n in a Gp A catalogue reveals that this header was originally produced for a Gp A engine in 2.3 liter trim. However, how the BMW Motorsport originally implemented this header is not entirely clear. According to Will Turner, the Gp A Rally header mates perfectly with a larger 2.5 L cylinder head. The factory boys may well have used this header on a hybrid engine with a 2.3 L bottom end and a 2.5 L head. According to Will there is another Gp A header which is different from the "Rally" header. In all, BMW Motorsport is reported to have produced up to 15 different headers for the S14 engine. The bottom line for me is that Will Turner has tested many of the available factory headers and has found that the Gp A "Rally" header provides a great overall combination of high end horsepower and low end torque.