Nissan Maxima 2004 6 SPEED

While driving on the highway I press the gas and it will not go pasrt 3000 rpms and seems to lose speed. It got tot the point where I couldn't gain any speed but then when I went it came back for a few seconds and I was able to accel. Also the car makes a loud noise like the muffler or converter has a hole in it. Sometimes I get a funny smell after as well. I hear it could be the mafs but I think its ore than that. Please help!