OK, Exhaust gurus, WTF is this on my 2.2 Sport rear box?

[DivideBYZero]

Please take a look at the attached pics. It looks like it's one of the sound changing vacuum based valves, but it's hard bolted to the rear of the back box. Odd.

Anyone?

 

[GazHyde]

It's a weight. It's there for balance or to cut down on resonance or something like that.

 

[DivideBYZero]

Hmm, OK. So an alternative to a Helmholtz chamber. I may just unbolt it anyway and see what difference there is. The 2.2 exhaust is pretty boomy by my standards, and I have an e92 M3 V8 with a modified exhaust...

 

[Stevo7682]

It there to stop resonance and vibration

 

[DivideBYZero]

I still want to take it off. It'll reduce car weight by a kilo, too!

 

[Alan W]

It's a tracking device lol...