Exhaust/Emissions experts please!!!

Ok so I am cleaning (attempting to at least) out my garage and glaring me in the face is my stock h-pipe and BBK o/r h-pipe. Now, I live in Michigan where we don't have emissions tests, so my o/r X can stay! In Michigan, having cats on your stang is considered unpatriotic! But, I don't know how long I will be in Michigan for, or even if I will take the car if I leave. I might give it to my father, I might take it wherever I happen to go. Obviously depending on whether I take it with me, I might end up in a state that has some sort of emissions tests, maybe CA or NC. So I might need some sort of catalytic system.

So my question is, do the high flow cats really work? Will I be able to pass the emissions test with them? Because I really want to get rid of my two excess h-pipes!

Thanx