read my quotes above.
this was pulled from a sticky on LS1tech created by a Mod.
""Header Basics by Loren Barnes, President, S&S Headers, Inc.
You have probably heard words like: back pressure, scavenging, tuned length, merged collector, rotational firing order, compatible combination and many others that meant something, but how they relate to a header may be a little vague. This article should give you a basic understanding of how a header works, what the terminology means, and how it plays a part in the header’s performance gains.
The first misconception that needs to be cleared up is that a header relieves backpressure, but a certain amount of backpressure is needed for optimum performance. Just the opposite is true. A good header not only relieves the backpressure, but goes one step further and creates a vacuum in the system. When the next cylinder’s exhaust valve opens, the vacuum in the system pulls the exhaust out of the cylinder. This is what the term “Scavenging” means.“”
yes, back pressure does matter but simply just putting on long tube headers per say on my car, takes care of the back pressure. I could run open headers for all I wanted and wouldnt loose any back pressure, but with a muffler like i have now, I Gain back pressure…so Im already adding onto the back pressure that my car already has.