Street Friendly (And California Legal) GD Subaru STI Build! Part Three, Getting Some Green Power With Cobb Tuning

Although our home state, California has great food and possibly the best weather in the county, the regulations that govern just about everything here have made about anything you want to do that’s fun illegal. Those includs modifying cars. Most of the stuff we do here circles around track-driven cars but this mini-series has been all about daily practicality. In California. to be street legal, mods have to have a CARB (California Air Resouces Board) Exemption Order number or EO #.  This means the part has been thoroughly tested in a CARB-certified lab and has been certified that it does not increase emissions.  Cobb Tuning has come out with a CARB legal complementary parts package that is suited for the majority of performance enthusiasts, especially those who live in California with its draconian laws.  Cobb also has performance solutions that are federally compliant and good for the other 49 states.

There first part of the CARB Legal package is the Cobb Cat-back exhaust.  We are very thrilled at the qualify of constriction of this exhaust.  It is up there with high-end parts from Japan.  The Muffler is a straight-through design with a perforated core.  This type of muffler has the lowest backpressure possible. The muffler’s bigger case volume gives more space for noise attenuating stuffing surrounding the perforated core.  The muffler has stamped formed end caps tig welded to the body.  This is superior to your typical roll crimped muffler endplate.  It also gives an attractive smooth look to the muffler body.  The muffler like the rest of the exhaust has a unique satin matt finish that looks better to us than your typical polished muffler.

The muffler has gusseting to the tubes to reduce stress on the muffler’s body.  The bends are beautiful pie cuts with perfect tig welds.  The hangers are headed so they won’t slip out of the mounts just like OEM and are tig welded to the muffler body and exhaust tubes. The hangers have long points of engagement and where they are welded to the thinner material of the muffler body, they are first welded to a doubler gusset to spread out the load to prevent cracking of the thin metal.  We have never seen that kind of attention to detail before, even in really expensive exhausts.

Look at the amazing workmanship of the Cobb exhaust as apparent in the flawless welds of the bends.

The exhaust comes with a burned Titanium tip that is fore and aft adjustable so you adjust its relationship with the end of the bumper.


  1. I know there was a lot of complaining when Cobb decided to pull a lot of their parts recently, but I’m excited to see what they can do while still being CARB compliant, especially with Flex Fuel and down pipes. Hopefully this owner decides to do more if/when the Project Green Speed development is fully fleshed out so the readers can get a no BS article about what is and isn’t possible while following the rules. As dumb as they sometimes may be…

  2. Thank you for the great article. Do you have any recommendations for an aftermarket turbo intake duct? There are a number of options on the market. I’d love to know what your experience has been with them, which is your favorite, and why.

    It looks like the resonator chamber had already been removed from the fender. Cutting out the back of the air intake duct, as mentioned on page 9, seems like a good idea, especially if the resonator is gone. But, wouldn’t you also recommend blocking off the two giant holes in the inner fender wall which, without the resonator in place, expose the air cleaner to all the road grime blowing past the fender liner?

    Thanks again for the excellent content!

  3. I see you used the COBB titanium cat back, is this similar to the older COBB catbacks that neck down to 2.5′ at the area that mates to the downpipe, or would this be a true 3′ all the way through?

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