2001 c70 - just purchased - loud noise?

[Fendar]

Hi! I'm hoping someone here can help me. Thanks to this forum I just fixed muly abs module and cleaned my MAF. Now another problem I have is the cars noise. As I accelerate the "roaring exhaust like noise" gets louder and louder as my MPH increase. It sounds like a nice tuned exhaust kind of, except it fluxuates with acceleration rather than RPM's. The noise sounds like it's coming from the front of the car, and MPH is the only thig that changesthe noise, turning doesn't affect it. Also the tires are practically new, but I haven't had them balanced or anything yet. Thanks in advance for your help! 1 more thing, the car has 80k miles.