Project GD STI, Fixing all the Details!

i-Wire makes a cool bracket that moves the Cobb overflow bottle upward so it is easier to service. It directly replaces the Cobb bracket.

The Process West intake manifold has a big plenum and moves the throttle body back toward the firewall.  Because of this, we had to fabricate new charge pipes as the Greddy ones didn’t fit anymore.

Underneath we used all of the manifold pre drilled holes for the power brake booster, evap purge, fuel pressure regulator, blow-off valve, wastegate, map sensor, and intake air temp sensor.

The IAG big throttle body is slightly longer than stock so you can see how the custom charge pipe has to make a fairly tight turn to clear the firewall.  HPS makes a wide variety of heavy-duty multi-ply couplers and this made our job of getting the charge pipes figured out much easier.

Contrary to what many people told us, the IAG motor mounts, transmission mounts, and pitch stop mount did not increase our NVH very much.  In fact, it was sort of difficult to ascertain if they were much rougher than stock.  They did stop any wheel hop or jerkiness from the drivetrain moving around.  The reduced movement is also much easier on the drivetrain in general and should help reduce breakage.


  1. I don’t think you are correct about the surge tank being mounted higher than the factory one. It’s mounted lower than the top of the cobb AF box and the stock is mounted almost level with the top of the intake plenum.

    It looks nice no doubt but it’s not higher than the stock one.

    1. We had a stock STI in the shop that I could actually measure and you are right, the top of the OEM tank is higher. The bottom of the IAG tank when the hoses attach is higher than the OEM tank bottom. The main reason we used it is to clear the process west intake manifold. Thank you for pointing this out and I edited the story to reflect this.

  2. Hi Mike!
    Do you think the lack of increased NVH from the IAG mounts maybe because of the increased chassis stiffness from the Cusco bracing? It would be interesting to test this out with and without the braces.

      1. Apologies, I did not mean for you to test it yourself, as I am aware you must have a busy schedule. I was just thinking out loud as that would be an interesting data point to test in the future ( possibly by me ). I do appreciate theses awesome articles you and your team have put together for free and I am building my STi very close to your build which is why I love to geek out on this stuff 🙂

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