Alot of this here is false, you live in california, we have the strongest emissions laws. NO you CAN NOT remove a cat unless it has been proven by a qualified shop that it is bad. You CAN NOT use a universal high-flow cat, it has to be CA approved. No exhaust or repair shop can legally remove your cat or any other emission device off of your vehicle. Visual inspections are very strict and they will inspect very closely if it looks like the cat or any other devices have been tampered with.
You CAN pull it, hollow it out, or put a test pipe in, however it is ILLEGAL, so do it at your own risk.... There is little to no performance gain on a stock/mild engine from a good cat to no cat at all. a bad cat has obvious issues that you cant use to compare anything.
Good luck on your decisions, Ca does suck for the stipulations they have on emission equipment.