What's this on my exhaust?

[Brooky90]

Hi everyone, my father in law came over yesterday and before he came in the house he was checking my car out. Five minutes after coming in he asks what's that thing sticking out on your exhaust? I said what thing? He said you got something else sticking out at the side. Anyway I've got a photo to show you guys as I don't know what it's for myself lol so hopefully someone can tell me.

[E-bmw]

Vacuum operated actuator for flap inside final exhaust pipe.

Several cars have them, most notably an e36 328.

[AdeTuono]

It's a homing device/tracker. They're after you...

[SlimJim16v]

IED?

[dudleybloke]

AdeTuono said:

It's a homing device/tracker. They're after you...

This.
Most likely fitted by "them".

[Tony1963]

One thing for sure, it’s fugly.

[Chiswickboy]

E-bmw said:

Vacuum operated actuator for flap inside final exhaust pipe.

Several cars have them, most notably an e36 328.

My E46 330 Ci has one but it is on the top of the pipe, not showing underneath as the OP's.

Apparently they are a vacuum operated flap valve on one of the tail pipes to cut down on exhaust noise when flooring the pedal. They often seize up and fortunately mine seized in the open position.