4-2-1 vs 4-1 headers
 

Which one is better?
Who makes the 4-2-1 and who makes the 4-1? (UEL and EL regardless)

Any thoughts? I am in the process of deciding to buy a header but not sure which one is better, and why! "Just because i have it and sounds awesome" type responses won't cut it ;)

As a generalization, usually the 4-2-1 helps mid range, 4-1 helps higher up. That being said it seems 4-1 is more common so far but not all 4-1 collectors are created equal.

From what I can recall the Nameless header is the only 4-2-1 long tube header while the P&L and FA20Club are 4-1 long tube headers. I believe most of the rest are not long and don't seem to perform quite as well. That's just what I've seen in general browsing around. There may be exceptions to this.

For a DD, I am leaning more towards the 4-2-1 headers, my car will not be seeing redline everyday like a race car would so the gains a 4-1 header gives me will just be wasted. After seeing the Nameless dyno, I am convinced that the way I drive and the mid-rpm my car sees daily will benefit from the 4-2-1 headers whilst benefiting the top end better than a stock header.

So do what works for you, because what works for me way not work for you.

The P&L header is trumping the 4-1 theory by both making a bigger top end and at the same time eliminating the torque dip. Pretty badass and if I were to decide to stay NA that's what I'd buy.

Long tube usually refers to the runner length before the merge collector. I definately would call the Nameless longtube.

Where can I get the P&L or Nameless headers from?

I'd consider the Nameless, P&L, and FA20Club all long-tube designs. I'm running the FA20Club header and it added plenty of low-mid range torque. I'm hitting the dyno on Saturday.

Is there a tuning solution for CEL when an aftermarket header is installed?

HKS is also a 4-2-1, doesnt seem to be to many of them actually around yet

The Nameless isn't available for purchase yet, while you can find a link to the P&L groupbuy in my signature.

I believe he was meaning that some of the other header designs as well as the UEL headers would not be considered long tube headers.

The nameless definitely is yes.

4-2-1 traditionally creates a broader torque band and 4-1 a higher HP but a peakier torque band. However most high level race cars i've seen run X-1 type header (x being the number of cyl) and good race teams say its area under the torque curve that makes a car fast. So i would have to say its more down to the design of the individual header rather than its configuration that matters.

Also why are the P&L and FA20Club headers considered long tube? The runners are shorter than most of the others on the market like the JDL ones for example.

i would've thought that they both produce significant power but the only difference is the torque "location". It seems that 4-2-1 would (as you said) provide a broader torque band, especially on the low end, while 4-1 will provide more on the high end and high speeds. I've just finished reading this:
4-2-1 Headers
As the name implies, the headers start from 4 pipes that merge into 2 pipes and those merge into 1 pipe.For most cars, this design produces more mid range power with the sacrifice of top end power. Mid range power is great for the street since when you drive you usually do not rev your motor close to redline. Instead, you keep the revs somewhere in the middle, usually shifting at 3-6K, and this is where the headers shine. Do note that not all 4-2-1 headers produce more mid range power at the expense of top end. Some high quality headers are able to improve top end as much as they improve the mid range. This is more the exception than the rule as most headers that are 4-2-1 do produce more power in the mid range, so the "seat of the pants" and "butt dyno" make these headers feel stronger since the power band isn't as high in the RPM range. This goes the same for both 4 cylinder and 8 cylinder applications. Since on a V8 the headers are 4 cylinder per side, you would simply have two 4-2-1 headers, one on each side.
4-1 Headers
4-1 headers are designed so that all 4 exhaust pipes merge into one. In most dyno tests, this produces the most top end power since it usually offers the best flow characteristics for the engine at high engine speeds. 4-1 headers usually move the power band up, which makes the bottom of the RPM band feel a bit weak and the "seat of the pants" feel might not be as strong as a 4-2-1 header. However, dyno tests have show that at low RPM there is very little difference in power. The 4-1 headers usually have less back-pressure than the 4-2-1 header and customers have stated their cars seem louder at high RPM with the 4-1 headers. Most headers that are street legal or CARB legal are usually of the 4-2-1 design but there are exceptions.