I think my cats are clogged and I don't have to pass emissions, so Im going to take them off. I was wondering what the diameter is going to and from the cat so i can but the pipe ahead of time.
Also do i have other o2 sensors before or after the cats?

 

I believe it's 2 1/4" before the resonator and 2.5" after the resonator. As for 02 sensors? I forget.

 

wheres the resonator?
I have 2 headers coming down to cats, then connecting to a Y to the tail pipe.

 

Minifolds down pipes 2 cats y pipe mid muffler pipe rear muffler.
I always thought it was a mid muffler not a resonator