High Flow Cats

Originally Posted by Togo

In CA it's a toss up whether or not you want to get them. HFC are illegal there as well as Test Pipes so you're technically screwed either way if a cop looks and is capable of seeing them. This car is pretty low and it would be fairly difficult to get a good view under there, I would think, but I wouldn't rule it out. Granted this is also assuming that the cop can tell the difference between stock and aftermarket but the lack of heat shields is usually a dead give away.

Now with a HFC you may actually pass a smog sniff check but not the visual, which as I understand it, some places often just skip. With the TP you will NOT pass a sniffer and certainly not pass a visual. There are obviously other methods of getting past smog checks but that may or may not be something you are interested in doing.

As far as gains go, Test Pipes net more power but not a whole lot more. Dynos have shown TPs to gain between 1-4 more HP than what a HFC will gain for you.

If you want TPs look at the Fast Intentions (F.I.) or the GTM ones. They offer extended O2 sensors so CEL shouldn't be a problem with them. They also offer them resonated so that you don't get a raspy sound in your exhaust.