So I've read some threads about using low flowing gas (butane or propane I believe) to check for vacuum leaks. But since I don't readily have access to either of these gases, is there an easier way to check for vacuum leaks?

Working in the engine compartment, when I slowly open the throttle I hear a hissing that sounds like air being sucked in through a small space (somewhere along the intake line) but even after checking to make sure all the connections are tight, she still hisses when the throttle opens.

Is this even a leak? I'm thinking it might be since an abrupt full throttle (like punching the accelerator) causes the engine to stumble a bit.......