Made a little progress today.
Below: The KLR tube extended 13 inches into the engine bay on my original harness, so I marked the new one at 13" and pulled it through the firewall snorkel to that mark.
Edit: after installing the intake, I would shoot for 14 or 15 inches instead. 13" works, but just barely.

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Below: On the cabin end of the tube, the banjo that connects to the KLR box is a type of compression fitting. I had to warm the tube up with a heat gun (not too much) so I could push it over the barb on the fitting. This is how far my original factory tube was pushed on, so I tried to copy the factory.

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Below: Then I just screwed the compression piece on all the way, and it's likely the most secure vacuum connection on the whole car.

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Below: I opted to put the harness in from the engine side. I fed the main DME and KLR connectors through the hold in the firewall, along with the smaller connectors on the cabin-side of the harness (e.g., altitude sensor, red 4-pin connector, diagnostic Kostal connector, etc.).

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Below: At first I really struggled to get the snorkel seated in the firewall. There isn't much room to work, and the snorkel is big and clumsy with a deep lip that needs to be seated on the firewall all the way around (much like a grommet, but on steroids). I ended up removing the end cap on the cam tower (the one with 3 bolts and a cork gasket), which gave me a bit more room to work. The other key was getting a lot of light on it, so you can see the rubber lip clearly. I used soapy water on the rubber, and first worked the sealing lip onto the drivers side of the hole (toward the center of the car). Once that side is seated, you have reasonably good access to the passenger side of the snorkel, so you can poke the remaining sealing lip under the firewall hole with a screwdriver or plastic pry tool. I gave up last night, thinking I may need to pull the cam tower, but with a good night sleep, a cup of coffee, and morning sunlight, I was able to get the snorkel fully seated in about 10 minutes.

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Below: This picture doesn't do it justice, but shows how the snorkel must be seated in the hole of the firewall. The groove for the firewall is quite deep, making that inside lip a pain to get seated. It's like pushing an 18" tire into a 15" hole. But it is possible!

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