yeah - the problem is a lack of empirical data and controlled testing - you get a lot of anecdotal stuff, but really nothing more than adrenaline fed subjective review
as an example regarding data, i have never seen a dyno chart of the header by itself compared to a stock car - the only charts i've seen are with an EVO intake and a chip, which showed significant gains - the butt-o-meter says it flows better and performs better, so it works out - how much is a question mark though - but that is one of the most fully tested items you will find for our car
a lot of this problem also stems from how things work together, so a straight comparison of say, a stock car to a car with a cat-back, versus a car with a cat-back and header, might not be representative of what you really get when you also add in a chip and airbox mod, and what you should really be comparing is a car with just the chip and airbox mod to a car with all of it
as for cat-backs, many mufflers have been tested - many different pipes - none show gains on a street car, and most show losses
the b&b posts claims of gains, though they have not been shown to make more than a couple of hp up top, and actually showed losses in the mids - the cargraphic was worse
i spent about $11k trying to sort out cat-back systems, finally landing on something that worked for the NA setup i had, but now might change since i am supercharged - rs barn spent similar money working out theirs - we both had similar goals - good sound with no losses - to my knowledge theirs is the only system that shows no losses
that being said, there is a common misnomer about "back pressure" and what is really being referred to is flow restriction - you never want back pressure, but sometimes you want flow restriction - it all depends on gas velocity and pulse timing - typically when you speed up the gas flow, you gain upper end power but lose low end, but gas volume plays into it too, as does the pulse timing and shape of the pipes - the dual resonant intake complicates things on our engines, and makes the engine performance very sensitive to exhaust system changes - what works on other cars does not work on ours
then there is the whole "sound" issue - some people like a deep throaty sound, some like it smooth and mellow, some like it loud, others quiet, and still others can tolerate the "kazoo" sound that many systems make - it's all really very subjective - what i could deal with when i was younger, i can no longer tolerate
as i said though, this is discussed quite a bit in the section i referred you to
![[Image: laugh.gif]](http://www.968forums.com/public/style_emoticons/default/laugh.gif)
