Funny Idle

[Gerard330ci]

Hello All.

I,m a new owner of a 2001 330ci love the car, but I have just a few questions. The exaust on this car seems a little loud for me, especially when I first crank it over. The noise sounds like it's coming from the bottom of the car, and will usually go away after about 30 seconds .Is this normal? And also my Idle seems to be acting funny it doesn't matter if the Engine is hot or cold, it gives off an up and down surging, puring, makes the car vibrate type of situation, I almost feel like it might be a fuel filter or a spark plug issue, but I can't be sure and I'm trying to avoid the Dealer $$$$. And I'm hoping its nothing to serious. One last question, what is that valve inside one of the exaust pipes meant for? And what position is it supposed to be in, Open Or closed?

Please help me !
Gerard330CI