I haven't had the truck for long, been doing a lot of reading here, not posting.
I'm about to drive several hundred miles for a training course and be gone a week, so I dropped the transmission pan to inspect and change the filter yesterday. The Previous Owner said it had been rebuilt a little over a year ago, and the fluid level, color, and smell were fine, I just wanted to know for myself that it had been done.
Anyway, while I'm letting the truck idle and get up to temp to check the AT fluid level, I noticed a ticking coming from the passenger fender. As I walked to the back of the truck to throw another empty bottle of fluid away, I noticed a louder and lower tone ticking coming from under the truck, so I crawled underneath and found that it is coming from here:

I have no idea how long it's been broken. From the dirt inside, I would guess it was that way when I bought it back in November. I traced the vacuum line back up to here:

I know it's not where it belongs, but it was just hanging loose when I got the truck, so I put there to be out of the way.
Anyway, what I need to know is, should I be concerned? Is it safe to head out for the week with it like that? and could this have anything to do with my poor mileage?
I have replaced the plenum plate (eBay plate recommended here) installed a K&N CAI, Gibson shorties, 3" SISO Cat, and 3" single exhaust all the way out. I had hoped after all that, I would be getting better than 12mpg.
Thanks in advance for your help.

 

its not a serious concern unless your truck is stored inside, where gasoline evaporation fumes might collect and ignite due to furnace, hot water heater, welding, cutting, etc.

you likely have a check engine light on? with code 442 or 455. someday when you feel like it get a replacement from the junk yard and hook it all back up.

the ticking from the passenger side fender area is the evap purge solenoid trying to empty the fumes. it should only do that occasionally for a short period.

 

Thanks DH, my truck stays outside, and I don't have a CEL, so I guess this will be a fix for later on.
Any thoughts on if it makes any difference for mileage?

 

its for gasoline evaporation containment only- safety and emissions.

there should be no difference in how it runs or mpg - unless you have a second problem with the purge solenoid. the purge solenoid is supposed to occasionally open up its valve between the canister and the intake, to allow the canister vapors to burn in the engine. IF (and only IF) your purge solenoid was stuck open, then you'd have a vac leak to the manifold, and it might run lean, or ping. if that happened, the O2 sensor should correct for it. if you have any concern about that - plug off the vac line from the canister, at the purge solenoid or the intake.

i wouldn't worry about it unless you get a new check engine light/code, or it starts pinging.