Hi guys i bought this R56 S a few month ago and found out there is an unplugged plug right under the intake and i can't find where this thing goes or what is for. I took some pics from under the car and from the top

 

Do you have a check engine light? There are a few possibilities for type of connection, its either evap solenoid/fuel tank vent valve (cant remember which is under the intake manifold), or its for the knock sensor's. Depending on where you're located and the model year, it could also be for crankcase venting heating . If you have a CEL and you can check the codes it will likely point you right to it . It looks to me to be the connection to the valve for evap emissions system under your intake manifold though, hope that helps.
dthtrp

 

I have CEL 2883. My mini is a 2008 cooper S, there is another piece back there but is connected. Where ever this plug connects my not be there, i just don't know where it goes or the name of the part

 

Yeah,
P2883 is a generic fault, and would point to the fuel system.

Check the vent solenoid which is tucked into the plenums of the intake manifold. The best way to see if its connected is to remove the air filter box and look through the hole in the middle of the intske manifokd between cylinders 2 and 3. If the vent solenoid has a connection plugged into it, then look at the knock sensor's on the back side of the engine block. There should be one behind the starter and another closer to the water pump. If they have are plugged in then I don't know what to tell you haha. Hope this helps.
Dthtrp

 

I'll check that today, it looks to me it's for the knock sensor because i remember i saw the vent solenoid. I'll keep you updated and thanks for all the help.

 

I found it; it was that evap solenoid and CEL is gone but when the car is at idle it gets rough sometimes and i have now 2 DTC showing Generic P1497 and Enhanced 2B64