Having some what of a huge problem with a 96 GT. Please help!

I dont know what it is. I turned it on today and it sounded very weird. It's making a tsss tssss tssss tsss noise. Its coming from under the car. It was fine when I drove it Friday night. My dad drove it Saturday and he said it was fine, I have a couple sounds clips but you cant hear it very well because I got them with a crappy cell phone.

One thing for sure im thinking it could be would be the mid pipe. I made a thread a while back when my clutch blew up. Well when it happened it dent the hell out of the left pipe that connects to the manifold. The guy that put the new engine in didint even straighten it he just weld it together. Maybe that could be it?

Any help I will greatly appreciate. I hope its not the engine, im in college right now and I cant afford to fix that. Plus im like 200 miles away from home

Please help

Heres the link to the clips

http://f1.pg.briefcase.yahoo.com/bc/ace_xbox@sbcglobal.net/lst?.dir=/Mustang

Im hoping its not serious. But I just read a similar thread. It doesnt seem good

Any other ideas?

*cries*