Exhaust Crossover???

Hey again guys. Okay, I know what an exhaust crossover is in dual exhaust applications, and that theres the X type and the H type. But my question is what is the purpose of it? I know that you get different sounds with the X, H, and none... but is that the only purpose of the crossover is to change the sound of the exhaust or is there more of a function that I'm not understanding? I was looking to buy a second flowmaster muffler for my Caprice for the dual exhaust, but while reading about it said "Crossover strongly recommended in dual exhaust applcations." I can't see how a pipe connecting the two separate exhausts would increase horsepower. If anything I'd see it as a decrease in power due to an interruption of the airflow.

Im about to put the same system on my 84 caprice classic that you are talking about . Im going to run 2 flowtech longtube headers , not cats , h pipe and 2 40 series flowmasters . However I dont kno exactly the difference between the H pipe and the X pipe although I kno different people have different preferences of which they use. I think I have heard somewhere that it equals out the tone having an H or X pipe .

http://i175.photobucket.com/albums/w152/capriceridin84/Picture045.jpg

The "H" pipe is referred to as a balance pipe - it balances out the pulses in either exhaust system by providing almost two systems for each cylinder. This in turn reduces backpressure, increasing scavenging and freeing up the exhaust sytem. An "X" pipe does the same thing, but provides less restriction.

I would never run a dual setup without one or the other. While the "X" setup offers the best performance, the "H" setup is almost as good and takes less space.