Just read a little more into manifold design, It would appear that what I read earlyer about pairing the primary headers isnt stricktly right. Read this!
"How the Header Primaries Are Paired - Sequentially versus Non-sequentially:
the ignition firing order determines which exhaust pulses leave in a particular order. In integras it's cylinder # 1,3,4,2. How we pair the header's 4 primary tubes together at the first header collector determines the horsepower vs rpm curve's characteristics or shape. Sequential pairing allows for a broader powerband and better acceleration properties from an engine.
You can look at your header and see which tubes are paired together: Is it sequential: 1 with 2, and 3 with 4? Or is it non-sequential? 1-4, 2-3?
The reason sequentially pairing of header primaries works is due to the energy imparted to the exhaust charge. If you just do 180 degree timing on the exhaust side, the exhaust pulses are evenly spaced, and they do permit a certain amount of "tuning", as opposed to just dumping everything into one collector.
When you space the tubes so there are more sequential pulses, the energy from one tube will have a much greater impact on the cylinder it's paired with, and the combined energy will have a much greater effect on the other tube it merges with.
Even (non-sequential) spacing (i.e. pairing header primaries from cylinders 1 with cylinder 4 and pairing cylinders 2 with 3) is nice and smooth, but pairing sequential pulses provides more energy to work with.
It's similar to the use of two single cylinder 2-stroke engines. If you want long running and smooth operation, connect the engines where they fire at 180 degrees to each other. If you want ball-busting acceleration, fire them together. It's all energy.
You get the same amount either way, but the combination you pick will allow you to properly select the energy spread.
On the exhaust side, you're dealing with waste heat, so if you can make it help scavenge other cylinder(s), you're simply not wasting as much energy."
