I wasn't trying to be funny or anything; jeez. There wasn't alot of information to go off to begin with. I realize that there could be a leak from lots of places and not just internally. No need to fly off the handle! Sorry, OP for leading you down the worst path. Check for obvious leaks...
When you're car is idling, try spraying some starter fluid around the intake manifold and gaskets and if your car starts getting rev-happy, then you know you have a vacuum leak somewhere.
I just bought a downpipe and AEM wideband and installed them a few days ago. My downpipe came with the bung and you could see it from the top of the motor looking down the back side. I think its a good location that way the harness has a straight shot into the cabin.