Don't have emissions testing here, but I've been wondering, has anybody thought about putting in a 2nd cat behind the first one ? Like go to the junkyard and pickup a cat - add some flanges or some Quick Change setup & stick it in. U could always take it out if you don't like it or whatever. Looks like, if one works - two would work better. It doesn't even have to be off the same type car. ( - jackup ur 'Marao and stick a cat from a Dodge Magnum Truck under there) Don't think you'd have to sweat any emissions test.

 

Mustangs actually have four cats,you just have to make sure the
second cat gets hot enough.