Howdy Mantoe and All:
I'm real new here. I've had my 2.3 '04 ZX3 for about 6 wks now. I love it, but not so much it couldn't be improved on. My first mod was the lunchbox delete and the addition of a nice exhaust tip. I can report a slight increase in exhaust volume, and a reduction in weight of almost 10 lbs. I can't honestly say I notice any increase in performance, and am still testing for any change in MPG. IF you don't plan on a Flex (AKA the "cat" in Duratec speak) back exhaust, the lunch box delete is cheap and a slight improvement in sound.
That's my two cents, for what it's worth.
Adios, David