Why is my exhaust making this sound?

What is your question?

I recently had some exhaust work done to my BMW M235i and after getting it done I noticed it had started to make a more or less a wind/vacuum sound from the exhaust. The exhaust was done with a y-pipe. Aside from that the car still has stock resonator, stock cat. and stock intake. Could it be one of those or could it be the exhaust work that was done?

What makes this problem better or worse?

It worsens at full throttle, but sounds fine sub 5k RPM

How long has your 2016 BMW M235i xDrive had this problem?

Couple Days