Project GD STI, Fixing all the Details!

Our new engine reused the MXP header and up-pipe, the Greddy oil cooler, and HPS hoses and hose clamps we were previously running.  Our IAG oil pan clears our headers easily. Unlike some Subaru aftermarket pans, the IAG pan clears most aftermarket headers, including our 4-1 system. You can see that the IAG deep sump pan has plenty of ground clearance and is not the lowest part of the car’s undercarriage.  It’s under the cross member so it’s really safe from off-road impacts.

The Cobb 3″ catted downpipe has great construction quality and fits perfectly.  There is plenty of clearance around the car’s underside and it tucks up nicely for good ground clearance.

We installed COBB Tuning’s stage one drivetrain kit which consists of their adjustable short shifter and hard bushings for the shift linkage and shift stabilizer linkage.

The hard urethane Cobb bushing is on the top and the deteriorated soft rubber stock bushing is on the bottom.  You can see that besides being old and cracked, the stock bushing has flex-inducing voids.


  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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