Pictures of my cars underside: http://smg.photobucket.com/albums/v3...aust%20system/

From headers to dual cats, then a Y pipe single to muffler.

Headers==dual cats>-----muffler<==dual exhaust

Because of the dual cats, does that not mean i could run a single pipe from each cat legally or because it goes to a y pipe, it would still be illegal to go true duals?

And how does the physics work behind an X pipe: Would having separate exhaust pipes for each header be better than converging into an X pipe?

passenger header---cat---muffler---tailpipe
driver header-------cat---muffler---tailpipe

OR

passenger header---cat\_____/muffler---tailpipe
_____________________X pipe
driver header-------cat/_____\muffler---tailpipe

I read about how an x pipe smooths out idle and evens the exhaust notes. i also read that when installing an x pipe, you need to place it in the right location to benefit from it over it being detrimental.

"One way to tell where to put center point of the X or install the H, is to take high temp spray paint and put a light coating on each pipe. Driver the car to get the pipes hot, then look for where the paint is bubbling off.....that's where it goes!"

 

Almost certainly you can do anything you want after the cats. The easiest mod is to put the X-pipe right where the two pipes join after the cats then run single pipes to two mufflers.