x and h pipes

It appears I was mis-understood, or did not explain it very well. Basically what I tried to say was that Both the "H" and the "X" will be a benifit in the flow and a slight gain in power due to the better flow and equalized pressure.

The "X" system compared to the "H" is relatively the same except in the higher RPM range, the "X" is better (slightly) than the "H", again due to the flow.

That is why todays cars have factory "X" system, they are higher revving engines from the factory. It is not unusual to see factory engines rev. above 7,500 rpm easily, compared to our older pushrod V8's and head design that need work to get in that range.

Having said this, I'm not saying that the "X" is not good in the lower ranges, but it's cheaper and easier to do an "H" system, if you are not going to be benefitting from it.

I used the highway/4:10 gears for an example of high rpm.

Sorry for the inconvenience this may have caused.