If you chose to go 3" with the test pipe, don't bother with a performance header, wait till you go KADET.
Stock header will help with back pressure and low end torque.

iite cool so KA24E (N/A) plus 3" from exhaust manifold back = pretty good setup ? :D

Personally I don't recomend 3" exhaust for any type of N/A, 2.5" keeps the engine quiet from noise violation, also gives a nice curve on the dyno. But if 3" is all you can get your hands on you should be fine as long as you use the stock header.
Atleast your pipe will be preped for your turbo setup.
But your 3" will be LLLLOOOUUUUDDDD, especially if you already have intake and filter.

With the removal of the CAT you should show a significant gain in HP, removing the CAT drops engine temp........

i was going to get a custom made 2.5 to a Apex N1 muffler but then when i decided to go Turbo i decided 2 get 3" so i dont need to change stuff later on and spend more $. im broke juss doing this setup :D

so your saying stock headers will have more power then performance headers with a 3". I personally like the low rumble my exhuast has. It's not to loud but it's loud. and it doesn't sound like a damn neon with a fart can.

No, stock headers are to manipulate the power band it has nothing to do with the gains. It is to prevent what is called verberation/vibration "pulses" that "WILL OCCUR" with a 3" exhaust on n/a. Literally it will make an un even flow rate through the exhaust system, actually dropping torque and HP.
The stock header will make the flow rate a little more consistant and regulated thats all it will do, it is to help keep the balance of backpressure.
If you just add performance headers with a 3" exhaust you are increasing the flow rate too much, and it will begin to slow down in the 3" pipe, it makes it unregulated, and causing major scavanging issues.
The engine uses back pressure "form of scavaging" to add more power to the compression stroke, hense making the downward stroke " on ignition" more powerful increasing HP. To much scavanging will cause exhaust gasses to run back up into the intake mani, decreasing HP.

The reason why 3" exhaust is used on F/I is only to increase spooling time, enough backpressure "scavaging" is already made between the turbo, and engine in the Turbo exhaust manifold. Hopefully that makes sence.

interesting, so basically with a 3" exhaust 'im loosing hP. That sux. I wonder if i can get a guy i konw to make an exhaust for me. then just use my muffler and sh!t. I dunno....

And alot of torque.......

yeah my car seems to bog on low end

I don't know if that's the biggest load of garbage I've ever read, but it's close.

It sounds like you may have at one time run across someone who knew what they were talking about, and you misunderstood just about every concept they were trying the explain to you.

The engine uses back pressure to add more power to the compression stroke? How the heck is that even possible? Did that make sense when you wrote it?

That is like saying that holding in a fart helps you eat better.

-Justin

I swear that I felt more top end torque and hp thoughout the powerband when I added 3" exhaust with my intake... but that's just the butt dyno... even though before I couldn't take my friends integra, and now I smoke him.. oh well.

hahahaha it doesn't????

Guys, lets stop paper racing with the butt-dyno. "I think I gained X whp!"

In all honesty the only way you're really going to find out if you gained anything or not is if you take it to a real dyno.

As far as 3" exhausts are concerned, I believe that you're just losing hp if you're N/A. 2.5 is even pushing it N/A, unless you're making decent power, lets say over 200whp.

In properly sized exhaust system, the backpressure is minimized as much as possible while allowing exhaust pulses to line up nicely and provide a good trade-off between both low and high-end power. For most N/A applications this pipe size would be 2.25" in diameter. A common mistake sometimes talked about in "tuner" magazines is that you need some backpressure for the system to flow properly. This is a myth created by amateur testing methods. For an N/A car, a 2.25 exhaust will get the best performance out of any other sizes, bigger or smaller. So because it outperforms the bigger exhaust people just assume that backpressure was the key to success here. I'm telling you right now, they are wrong. The reason the exhaust performed the best was because the exhaust pulses were perfectly in line and able to draw each other out of the exhaust at the highest velocity possible.

I'd really go only 3" if you are turbo.

Another thing is...an exhaust system is just that. A SYSTEM. It works well only when other parts in the system work with it. Having a stock header might help to stop reversion, but WHY choke power from your system? All parts should be equal in diameter for optimum performance.

This makes me wonder why ANYONE would use a stock header, unless they couldn't afford something better? The restrictions of that header might help with reversion, but you're really choking the flow of exhaust gasses.

There are TWO goals of an exhaust SYSTEM (Yes, it's called a system for a reason)

a) to efficiently remove as much of the combusted inert exhaust gases out of the cylinder.

and

b) to keep the velocity or speed of the exhaust gas leaving very high.

Hope this helps you guys and clears up some things...

It's all about gas velocity and scavenging.

-Justin

How bout this call a couple of shops like Rebello Racing, or whatever top performance company comes to the top of your head. Give them a call express to them you feel a 3" pipe is better for N/A and get prepared to get laughed at......
Exhaust isn't like a fart the analogy isn't even the same. Sounds like you need to read some more books.....