Help something isn't right...
 

Was giving my car a little gas, about 4500rpm and I started to hear a hiss come from about the middle rear of the engine. Now when I press the gas I hear this hiss and it gets louder the harder I push the gas, there is also a big power loss??? I can't hear it when my head is under the hood only when i'm driving it, but it sounds like it's coming from the back of the engine. Any ideas?

Loose plug? Vacuum leak of some sort?

deff. a vacuum leak or exhaust leak....check all of your tubing