I recentlty bought a 2000 Grand Marquis with he handling package. When I bought the car the window sticker claimed 18 mpg city and 25 mpg highway. I have taken it on two long highway trips recently and the best I could do was about 18 mpg. Is this normal? Since I have owned the car, I noticed that when the car is in overdrive between 35 to 50 mph and I give it gas to accelerate but don't give it enough for the car to downsift the car will buck slightly until I make it down shift. Could these two issues be related? I have read that the Mass Air Flow (MAF) Sensor and Differential Pressure Feedback EGR (DPFE) Sensor are occasional problems with these cars. I am wondering if either of those sensors could be failing.