any power gains from header only?

I am going to keep my exhaust stock. Or, rather I should say I'm keeping my muffler stock. I think headers are part of the exhaust as a whole. Anyway, a guy at work wants to sell me a DC Sports 4-2-1 header and install it for me for like 130 bucks. I think that is a good deal but what kind of power gains will I get from just the headers? Any? Is it even worth it? I know any mod is worth it and I'm sure it would be better than stock but if I can't feel the gains then I might as well not do it and learn do out drive people if I can't out horse them. ya know?

the flow of the air into and out of the engine is VERY restricted....opening that flow up any way possible is always going to make power....but real power will not be realized until you uncork the entire breathing system....intake, headers and exhaust to start but eventually a TB, port matched intake manifold and a good port and polish sould really open an engine up. Just getting the headers is a good start but it wont get you a lot of power because there are still going to be bottle necks in the system as a whole! But hey everyone has to start somewhere wether its an intake by itself, headers by themselves or an exhaust by itself....there arent many people who w8 long enough to save all the money and buy everything at once...its a process....and thats why we love it

Sport Compact Car rated the DC 4-2-1 the best for the GSR because it gave the best across the board gains.
The stock header is apparently pretty good when matched up against alot of the aftermarket stuff.
Like Jngrbrdman said, any help to the flow of air helps, but you get the full gains from it unless help the flow in all other areas of your exhaust....

[2ndGenTeg]

Just a header? 1, maybe 2 hp.

As they said, your exhaust system is exactly that- a system. Upgrading the stock exhaust manifold to a 4-2-1 header will help, but you still the problem of that nasty 1 1/2" exhaust piping, creating a bottle neck.

Think of it like this. You've got a gallon of water flowing down through a pipe 1 1/2" in diameter. Now, you dump it through a traffic cone, in through the large opening, out through the small. Does the water reach the ground any faster? Not really. While the large opening in the traffic cone may be a foot across, the small opening is that same 1 1/2 inches. Now take a pipe 2 3/4" all the way through- that's how you're going to get the best flow.

You'd be better off taking that $130 and getting a generic intake.

I've already got the intake. I had a guy try to sell me an exhaust yesterday too. I wish that I was made of money. I don't know why people keep trying to get me to change my car. The GSR is fast as it is. I don't need a thousand dollars worth of modifications to be able to smoke Nissans. Even stock the GSR is a race even for an Si. I figure that keeping it stock is going to be ok for now. I like the intake because it is loud. I wouldn't want a muffler drowning out the intake anyway.