Any way to pass emissions w.o cats?

I have had my BBK O/R H for about a year now and here in WA we have to do emissions every two years. I am just going to swap pipes when I have to go through the testing.

I love the sound and it is a noticable difference in power to me but I am thinking about going with a high flow catted pipe just to be legal in case I happened to piss off a State Patrol here.

We'll see. I love the sound of my car right now which is something I don't wanna lose.

Before emissions should I have the stock pipe on the car for like a week or two?