I have a 2001 GT automatic with 47K miles. Only engine mods are a K&N intake kit and steeda underdrive pulleys which have been on for a long while. The problem is that the car often jolts while cruising along. It's most noticeable when trying to just maintain a low speed, holding it between 1000 and 1500 RPM. It's been doing this for quite some time. However, it seems to be getting progressively worse. I now can sometimes feel this jolting while accelerating although it's much less noticeable when I'm on the gas. The car is past due for a fuel filter replacement as prescribed by the recommended maintenance schedule. I plan to check the MAF to see if there is possible some oil from the K&N causing problems. Any suggestions will be greatly appreciated.