Coolant in 325i sports

Hi guys, time for my 1st post! I have 2 questions,

Firstly, my coolant light has just come on and I was wondering where I can find the filler cap under the bonnet!?

Secondly my sports exhaust that came with the car is blowing and I'm getting a replacement. I'd like it to be louder than standard but not rattly or droning. I'm considering either  a Powerflow cat back (as they can specify the noise) or a Sebring.

Any thoughts would be much appreciated.

Thanks in advance!

-Dan

As you look at the car from the front the coolant expansion tank is on your right hand side just beside the air intake box. Might not be low on coolant though, could be the coolant level sensor on the top of the tank, if it doesn't go out when its filled up then take the sensor out and check the connections and movement of the float piece inside.

The mongoose stainless steel system is very good, got one on mine, quite loud, sounds very throaty and not atall raspy or tiny, fit was good to, plus the twin 3.5" tail pipes look lovely.