Agreed Toolmanmike,
Here' s a great write up I found from Motortrend....
X vs. H
Although X- and H-pipes perform extremely well for a minimal investment in time and money, both offer unique properties that make one more suitable than the other depending on the application. "The two biggest differences between an X- and an H-pipe are sound and power. Generally, the X-pipe will deliver a more high-pitched exhaust note, making a car sound more exotic, whereas an H-pipe gives a deeper tone with more of a traditional hot rod sound," says George Rumore of Stainless Works. "As for the difference in power gain between the two, it is very minimal. The X-pipe will usually make anywhere from two to four more horsepower than an H-pipe. The slight horsepower difference comes from the way the X-pipe creates a venturi effect, which helps pull the exhaust gases out of the cylinder faster. Overall, the main difference is sound rather than performance, meaning there are no pros or cons. It's simply a matter of personal preference."
In addition to differences in sound and horsepower, both X- and H-pipes affect different parts of the powerband as well. According to PerTronix's Don Lindfors, the basic configuration of both styles of crossovers lend a clue as to why this is the case. "An H-pipe tends to make more of a difference at lower rpm, while-X pipes will increase power more at higher rpm. As you can imagine, just by looking at each configuration, in the H-pipe the exhaust has to make a sharp 90-degree turn, while the X-pipe offers a smoother transition," he says. "The X-pipe creates much more of a scavenging effect. That said, it is important to prevent the X-pipe from necking down too small or flow can be hampered. Both an X- and an H-pipe will smooth out the separated sound of the cylinders, while an X-pipe tends to blend all eight cylinders together more."
For all-out power, X-pipes seem to be the winner, but H-pipes boast several advantages as well. "H-pipes typically offer increased backpressure compared to an X-pipe, which nets an increase in low-end torque. They are also more tunable because they offer more options in terms of the length of the crossover, the diameter of the tube, and the size and location of the transfer hole," Blane Burnett explains. "As a simpler design that takes up less space, H-pipes have more options as to where on the exhaust system the crossover section can be placed. While performance is a large consideration when designing an exhaust system, vehicle packaging is also a huge factor. Depending on the application, an X- or an H-pipe might suit the chassis better, but an H-pipe certainly offers more options as to where it can be placed."
