Originally Posted by MADDOG
The gases are too hot in front of the cat to begin to pulse or "cross over".
An old racer's trick is to take some black paint and paint the inside of the pipes downstream of the headers. They also metal score a line in the pipe where the paint begins and ends for reference.
Then they go out and get the pipes good and hot. The paint burns off the pipe, from the headers back, and where it starts to cool off (the crossover point - the gas has slowed and cooled here, the gas pulses slow down and equalize) the paint is still there. That's the spot they cut in for the crossover pipe.
An X configuration is more efficient than the old H pipe arrangement as the gases follow the gentler angle of the X vs. the hard right angle of the H.
Obviously, where the X meets in the middle of the two pipes, it's an open chamber.
Not trying to kiss here a*$, but it's information like this that makes me glad I joined these forums. Thanks MADDOG!
I'm gonna' do a little research and see about gettin' an x-pipe fitted to my system now if it's at all possible.