whitch cat do i hollow out the main one if this is a dumb Q i am sorry

 

TII or N/A?
and if you got SMOG test's forget about passing if you do this

 

The dumbest statement or question in the world will not appear so if you fill it with proper and interesting grammar and vocabulary. I'm not saying I have either, but small things go a long way.

If you are hollowing out a cat you hollow out the main big one, closest to your seat area. But I would suggest hollowing out the precats as they'll cause more restriction than the main cat. Removing cats is illegal in 50 states. A straight pipe would create less turbulence and such. If you have an 86-88 make sure you have enough backpressure or a better way of actuating 5th and 6th ports.