Hard telling exactly. Exhaust shield rattling off the pipe? Collapsed passenger side motor mount?

You're going to have to get the car in the air and get under it and start inspecting/banging around on things, etc.

 

Hey! Just checking in with you if were able to figure out what it was? Having the same issue.. Replaced my rear motor Mount but nothing to the top ones yet.

 

Hey I'm facing the same issue any solution so far?

 

Oki so , had a very similar sound , was thinking I was just having wheel hop during quick acceleration was super concerned… changed rear motor mount to Cobb performance mount ( pretty tight fit on the sts comes with extra vibration s but reduces wheel hop like crazy ) thought my problem was fixed 2 weeks later same **** , realized my other mounts were ****ed too , top mount on passenger side under coolant was completely blown 😂, super easy to replace then … another couple of weeks boom last mount (driver side trans mount) my car making this mf noise again , so thinking bc I upgraded all other mounts to performance caused more wear on my stock mounts/bearings, after i upgraded all to Cobb and AWR mounts can confidently say this sound completely reduced as well a huge reduction in wheel hop …can’t say this is going to be the same fix for you but attempt changing all mounts typically When one is ****ed they all are , you can take the cheaper route see abt changing all your bushings in the bearings 1st but highly recommend going performance if you’re going to change all 3 anyway , you won’t have to change them out again .