Header Aftermarket FAQ

What changes will be made to the exhaust sound?
a. Equal length headers: there will be a drastic difference in the exhaust note. It will change from the boxer rumble to a more traditional engine tone. This can be negative for some people as they love the unique sound of a boxer engine.
b. Unequal length headers: there is generally mild to no sound (db) increase or change in tone. Any changes in unequal length headers are generally considered subtle.

I have or soon will have a twin scroll turbo, is that important for header choice decision? Yes. You must use an equal length header specifically designed for a twin scroll turbo, otherwise 100% of the twin scroll turbo’s benefits (earlier spool vs. equally sized regular turbo) are gone. While you could use an unequal length or regular equal length header with a twin scrool turbo, you now will have regular turbo spool characteristics or possibly worse.

Which header has the best gains? There is no irrefutable evidence that any header has better gains than another. The consensus, if there is one, is they are all within 5HP or less, gain wise, of each other. That being said, there are extremely wide variations in how each header affects the powerband. This will play a key roll in determining which header best suits your power wants in which powerband.

Are there any downsides to headers? Yes.
a. Some manufacturers’ early versions of headers had fitment issues, which could be cause for concern if purchasing a used header.
b. There may be a few manufacturers who still produce headers with possible fitment issues.
c. Increased in turbo spool time. The actual RPM reduction will/may vary with manufacturer/heat wrap or coating/overall header temperature but a good rule of thumb is around a 300 RPM increase (spool comes on later) in spool time.
d. Some newer headers are designed for the STi, so they may require WRX users to use the STi oil pan due to it’s different shape.
e. 2006+ saw changes to the placement of the oil filter which can interfere with header fitment, so discuss with your Vendor prior to purchasing headers as to wether they fit correctly or not.

Are there any other benefits from a header? This link contains some very interesting testing of EGT readings from a full exhaust and a header. The results seem to indicate the cause of high EGT readings is due to the poor flow/design of the stock exhaust/exhaust manifold. Though this information isn’t 100% foolproof, it offers strong credibility to the thought that headers+exhaust may be the solution to high EGT issues with modified vehicles.

Are there any do it yourself options? Yes. This thread contains a compendium of thoughts and experiences with port matching and port and polishing the stock exhaust manifold. Though there is a lot of theory and speculation there isn’t a whole lot of evidence to support this modification having the same impact as a full set of headers. It certainly is a cheap, do it yourself project with few possible negative impacts though. This thread contains DIY porting instructions.