Weird rattle/noise after messing with my exhaust

[DarkMaroSS]

Guys, I want to know what you all think.

I am hearing a weird vibration after installing a tru-X. I first installed two Magnaflow mufflers, and had no issues, but then a few weeks after decided to go for the Tru-X (still catted) and that's when I started noticing this "vibration".

Can't really be sure if it's the so called drone, or related to the AFM. I can hear it around the driver rear side. Checked for anything loose, and pretty much tight. The tunnel brace was taken care of with longer bolts, 1/2" x 2" washers, and polyurethane sway bushings, to make sure it wouldn't do any metal to metal vibration as I thought it was related to it and the heatshield, plus to add clearance, but still.

Basically, after leaving the house and deiving between lights around 35-45mph at almost no throttle (low rpm), I can start hearing it and when I let go off the gas after that. The weird part is that it goes away once the car is fully warmed up. Only does this when it's cold.

No drivability issues of course, no physical vibration related to tires or brakes. But can hear enough to drive me nuts figuring that out.

Any thoughts? Thanks in advance.

[FunkedOut]

check to see if any part of the exhaust is less than 1/2" away from anything.
the exhaust moves with the engine and may be contacting something.

if not that, you may have a loose baffle in the muffler.
grab a rubber mallet and tap the exhaust at the last bend before the muffler.
if something is loose in there, you'll hear it.

[DarkMaroSS]

Originally Posted by FunkedOut

check to see if any part of the exhaust is less than 1/2" away from anything.
the exhaust moves with the engine and may be contacting something.

if not that, you may have a loose baffle in the muffler.
grab a rubber mallet and tap the exhaust at the last bend before the muffler.
if something is loose in there, you'll hear it.

Exactly my thinking which is why I put longer bolts and poly bushings to space out the tunnel brace, but this one has 1/2" or maybe a little more. I checked the rest also, but dodn't see anything odd. Tapping it with a rubber mallet, I haven't tried that, but when I first took it to the shop after the install, they did it and it all seemed fine.

[TX_ED_SS]

Take a look at your heat shields as well.

[DarkMaroSS]

Originally Posted by TX_ED_SS

Take a look at your heat shields as well.

I will check that again once it stops pouring down here. I just got out from different muffler shop just to get a different opinion and they couldn't find anything either, which is odd.

What other issues have you guys had or read about from these cars related to exhaust, AFM, drone, straight-through mufflers, etc? Flow related, needing a tune, as I've read here? I've had this car since June 2015 and had no issues until I had the brilliant idea of messing with it.