Thank you andrewwynn and 13brian for your input.


Here's where I'm at so far:
The sound appears to be coming from the passenger side front near turbo
No mechanical fan
Happens at all speeds and RPMs

No DTC's or CEL's
It doesn't happen until engine is warm
Only happens when decelerating and goes away with slight acceleration
Not the waste gate
Not the transfer case or drive line

Didn't have this sound before EGR, swirl flap, def, dpf delete with 2.5 tune and VRSF downpipe. I replaced the thermostat as a prevention.
Other than the noise, it runs great. Drove 40 miles last week and just 2 footed it.
Going to do vacuum testing next week. I already replaced most of the vacuum lines last week.
Really stumped.