Re: Hi Flow Cats or Catless
Not sure about 318, but on 320, 325 and 330, you will have the primary cat at the headers/extractors. There is no way to remove that unless you change the entire extractors/headers. eg. HI-OP.
*NOte, this is the part where the lights may come on.
Then there is the secondary cat or resonators shortly after the down pipe. You can remove that without much sacrifice to the low noise level. eg, you can get any exhaust shop to cut and re-wield a straight thru pipe. MAn exhaust have high flow cat of all size too.
Third, there is a mid box (small) prior to the final rear muffler box. You can remove that but this time, your noise level will shoot up the roof. I will not recomend this. Some exhaust like the SS have their own mid box to replace your existing ones.
Forth, the rear muffler. Do as you please within legal means.
Best config will be:
Get Hi Op Headers, remove secondary cat/resonators, custom mid box and exhaust of your choice