Ok, I'm chasing a rather bothersome noise & random-misfire code, that I believe to be a top-end problem...

To do this, I pulled my driver-side valve-cover, to check if I had any rocker or spring damage... None evident.

In the process, I disconnected a very, very small vacuum hose that appears to follow the wiring harness (the one that runs along the side of the valve cover) down the front of the engine.

Where does this thing go to?

 

Sounds like OPTI suction hose if its about the diameter of a pencil.
Runs from the left side of the intake, from a nipple to the optispark.

 

Or the EVAP canister purge line.

Look at the vacuum routing diagram on the radiator cover.

Shoebox has an example:

http://shbox.com/1/emission_hose_routing.jpg

 

About the diameter of an electrical wire, but not a wire - a hose...

Will post pics tomorrow.

 

There is also a vacuum line that was added as part of the AIR system recall.

Courtesy of Shoebox:

http://shbox.com/1/air_pump_recall.jpg