whining noise from engine when acceleration hard

I have a 98 venture with 119000 miles, recently whenever I accelerate hard or press the pedal to the floor, I hear a whining noise, like something is squealing, and the van doesn't accelerate. It seems to be hesitating and it doesn't want to go past 60 mph. If I accelerate slowly it goes up to speed fine. Has anyone else experienced this problem?

Do you have a rotten egg like smell? You may have a plugged cat.

Do you have a rotten egg like smell? You may have a plugged cat.

That was exactly the problem, I changed the cat. converter today and the van works perfect. It seems like its running faster too.