I live in san diego, california. I have an 03 duramax that is 100% stock. My question is; does the catalytic converter installed on ca models restrict exhaust flow. The pipe looks like a thru an thru 3 inch but I was wanting to go for a full 4" straight pipe and eliminate the cat. I dont think I have to smog a diesel here but that yet could change. Does anyone know ca smog regs on diesels and whether or not i'll ever have to be concerned with reinstalling the cat if removed.