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

The Cobb exhaust is unboxed and readied for installation.

The Cobb exhaust weighs about half as much as stock.  You can see the large-diameter tubing and smooth bends of the Cobb exhaust compared to the stock part.

The front part of the new cCobb exhaust is bolted to the cat.

To be able to ship the exhaust UPS and save customers a bunch of money, Cobb like all other exhaust manufacturers, adds a joint to the exhaust so it can fit in a shorter box.   Cobb uses a slip joint with a band clamp to make a leak-proof, strong, and simple joint that doesn’t need gaskets.

The Cobb exhaust is now in place, you can see its large diameter and smooth free-flowing bends.

The final touch is adding the tip and adjusting its position.  We put the end of the Cobb tip in the same place as the stock part.


  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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