2006 8.1

I noticed today that I have a hissing noise coming from my the drivers side of the engine somewhere. I couldn't find out exactly. The question is, has anyone had a vacuum leak on these engines, and if so where was it? I am not sure if that is what it is, it just sounds like it.

The engine is not stumbling really, or idleling high or anything like that. At first I thought it was the fuel pump, but the noise is around the engine.

Any and all help is appreciated.
Thanks.