Noise at Actros MP2 Euro5

Now it’s so far for 2 days MP2 drivers nothing more TGA, my first Actros before only MAN or Iveco. Must not say bad so far. Just a little louder in the cabin like the TGA. But I can’t say about the rest so far. I’ll get used to the power shift circuit. Only one thing I’ve noticed negatively so far and that’s that at regular intervals gives a kind of exhaust noise while driving and in stand when I pour off fuel oil at the customer, he does so funny Is that the dosing unit of the AdBlue or is that the chemical reaction in the SCR-Kat. Have no idea what else it can be. Know up to now only EURO3. New truck what can be there already. Is somehow bad to explain because it is bad to describe. But maybe one of you can help me to drive the Actros longer. And in the stand when it is out of motor, it also does so funny that the air dryer is. Blow something out like that. stop, only it stops and comes back shortly afterwards. I didn’t know these things from the TGA, but I don’t want my TGA back, the MP2 left too much impression on it. New truck new “weary”. That’s how it is when you get a new truck. Thanks in advance, let’s see what this might be for a discussion.