What part is this?

2010 1GR-FE engine
Remaining part after replacing all the coolant hoses.

 

That's the vent cap for the ACIS VSV on the back of the intake.

 

Thank you for such a timely response, which allowed me to go find the location and install it.

 

I have been in and around the 2nd gen v6 with dumb levels of knowledge of the thing..... NEVER woulda guessed that answer.

 

Well I knew it looked like a vent cap for a vacuum solenoid and there's only 2 of those on a 2nd gen but the Purge VSV doesn't have a vent port so I figured it was the ACIS valve, looked at mine and I was right.

Makes sense it got knocked off because the heater hose runs right by it and the OP said they just changed hoses.

 

Anyone know what the consequences are if missing that cap? I just noticed that mine is missing after having the truck serviced recently. It seems you have to buy the entire ACIS VSV to get the cap.