Thanks to focusing on an in-car camera for the Evo’s events, I was able to notice that the CEL was flashing at various points in the upper RPMs during my track days, and even during autox. My tune is programmed such that the CEL will flash if the car knocks. Speaking with the tuner, he was convinced that this was due to a leaky EGR valve allowing high temp exhaust gasses to sneak into the intake during high RPMs, causing pre-detonation. I didn’t feel anything when the car did knock, nor did the UOAs I’ve been doing note any kind of excessive wear.

I bought STM’s stealth block off plate, which, instead of removing the EGR system altogether, sandwiches a plate between the EGR & the intake. This allows me to pass visual inspection of the EGR in certain states that require it (i.e., California), while still providing the benefits of not having an EGR. I used two gaskets, and probably too much exhaust sealant, and installed the piece. Hopefully using that much won’t come back to bite me.

I didn’t really take pictures of the process, and I couldn’t find instructions, probably because it was such a straightforward job, but (do all work at your own risk):

1. The UICP has to be removed
2. The battery will likely need to be removed, especially if it is stock or in the stock location
3. The EGR is located under the throttle body, and under some 3-pronged plate as well – took that one off by mistake the first time.
4. It is 2 12mm bolts, and will likely need extensions to reach it without twisting anything too much.
5. Put the sandwich plate in, and rebolt. May use gaskets & sealant, not sure how necessary it is.