This is the "discussion" from the "Tube Header Group Buy" thread which many have requested to be cleaned up. It starts off with this post (Aaron's) estimating a possible 40whp gain from such a product. - JT
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Dang JT, nicely posted. I think that covered what we discussed quite well!
Mr. Baker, it certainly is a worthwhile investment for anybody serious about wanting to make some big power. Even with the little 'ole papa smurf Daytona of mine it made up to a 15 WHP/WTQ gain above 4500 rpm. That is over a stock manny, not a ported one, but it's also through a 2.25" SV, with a stock head, stock intake, stock turbo (+ .63 housing).
On a well modified car I would see no reason a good header couldn't make a gain of over 40 WHP over top of a ported manifold.