Kid's 2012 jetta has me bamboozled

The daughter's jetta just recently started w a rattle sound that I can't figure out. Before I head into the stealership I thought I'd ask you guys and gals. 2012 automatic 6 speed TDI w 135000 miles on her. Recently when the car is warmed up & she gets into that 35 - 45 mph area while travelling strait and comes off the throttle there is a rattle/vibration that sounds like it is located low on just the other side of the firewall possibly to the middle/right side that w any steering input right or left will go away. I cant feel it through the wheel or gear selector at all and couldn't finding anything loose when I put her up on the stands.
All my years of driving this is the first issue I really am clueless on... it is of course the first VW I've ever dealt with also lol. Since the child bought the Jetta though I've been living and learning every day about German engineering ??
I have a video that you can hear the sound in I just don't know how to upload it.
Thanks for any and all help!!

It sounds like the problems I've had with the 2015's there's a bracket in a screw that attaches to the heater core pipes that go through the fire wall That rattles


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Thank you tdiman, I'm working the next cpl days but that connection will get checked out come Saturday!

The rattling on the 2015's is accessible right above the gas pedal


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