...Sometimes the car has a hesitation? when I give it gas. I googled this and it said it could either be a mass air flow sensor or bad vacume lines. How can I be sure before relacing the sensor. Also how diffucult is it to change the mass air flow sensor? The car has 120,000 miles on it. And while i have your attention what about spark plugs could this be a reason I have no idea when the spark plugs where last changed. Is it easy to change the plugs?