easy.
ill go through a whole process you should go through to see what exactly it is.
1st obviously pop the hood and turn your car on.
check to see if you hear and air leaks coming from any of your vacuum lines. also see if any have popped off.. if you hear anything, check the obviously lines that are out in the open, after that, check the 2 that are under your intake manifold, they tend to crack easy since they constantly get hot and cold all the time.
if that's not it, disconnect your maf sensor and see if that makes a different in how the car operates. if it doesn't make a difference then that might be your verdict.
if it does plug it back in and take on coil pack out at a time and see if that makes a difference in performance.
if its an o2 sensor it will be the top one since the bottom one only reads what is going in after the cat and doesn't control air/fuel mixture.
hope this helps a little..