Synacks

Description:
The vibration is located somewhere is the rear exterior half of the car. Likely near the muffler. It is triggered by accel or decel or free revving entirely by the loud vibrations of my larger exhaust. It is not exclusively triggered during movement. The sound can be heard from behind the car when a buddy is just free revving it.

It is a higher pitch that sounds like a cheap raspy exhaust, but everyone that has heard it believes it is a vibration caused by the exhaust, and not the insides of the exhaust itself.

My car:
174K miles MY06 used for the track, so I'm not putting stock exhaust or interior back together just to satisfy a vibration.
Aftermarket exhaust from header all the way back. Includes EVS HFC, a single exhaust with two resonators, and a quiet muffler.

Things checked already:
License plate
Tail lights
Exhaust touching things it shouldn't

afzan

drop the hfc and see if the vibration still happens with an open header?

Synacks

I have a test pipe I can swap in, would that be better?