2000 Chevy S-10 Exhaust is hissing

Noises problem
2000 Chevy S-10 6 cyl Four Wheel Drive Automatic

So I cut the catalytic converter off of my truck and ran a straight pipe from where I cut it to the tail pipe and today (10/7/10) it started making a very loud hissing sound when I hit the accelerator instead of the loud rumble it usually makes. I checked to see where the cound could be coming from and didnt see anything out of the ordinary except for when I turned the truck off cmpletely the muffler started making a cracing/ popping sond from the inside of it. What could be the cause of the hissing and popping?