91 Nissan Maxima exhaust/engine problem

[blahzay]

Today, I decided to floor it down a country road. The third time I was accelerating, I noticed an odd noise. At first I thought it was just the wind because my rear windows were open. I closed them but I still heard the noise. When I got home i figured out where the noise was coming from. It was coming from the exhaust and it was kind of a whooshing noise.

I even have a bit of trouble accelerating because on that third time when I noticed the noise, my car was moving like a slug and my foot was all the way down.

What is the problem and how much would it cost to fix?