Exhaust 4 Cats required for smog in California?

Codosuarus

New Member
Jun 6, 2021
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San Diego
I have a '91 GT that I upgraded quite a bit in about 2004 (before I had kids).
This included BBK shorty headers and an aftermarket exhaust system.
At the time, I did everything to make sure that I was california smog legal.
I have smogged the car every two years in california ever since.
I probably have put less than 10,000 miles on the car since.
I brought the car in for a smog the other day and the smog tech told me that 4 cats were required.
Now I remember this being mentioned back when I replaced the exhaust system and I dont remember any aftermarket exhaust systems having 4 cats.
But it has been so long that I cant remember what the solution was.
Can anybody remind me how these things were smogged with only two cats?
 
Car came with four cats from Ford so California will require four. Sounds like you got lucky prior to this.

Did the inspector ask for the CARB EO number for each piece of the exhaust system? If not then just weld two more in downstream of the O2 sensors and be done with it.
 
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Now, I [think] there is one other system out there on the market with an H-pipe that is California legal. I could not find the one I was looking for but maybe somebody else in the forum knows which one I'm talking about.

I did find this one though:


So, there are now two aftermarket, Cali compliant systems on the market that I'm aware of.

If I find the one with the H-pipe, I'll come back and post it.
 


Ohhh... I see. nevermind that one then.


There is still an H-pipe version out there somewhere that is 50 state like the Magnaflow X. I recall it being pretty pricey too.
 
I'm one state over from cali. And no visual just a sniffer test in the tail pipes every year.
I've used the same guy for smog since I got my stang 18 years ago, I think he likes her that's why.