OK, yesterday driving back to home from work I was revving to 5K and then all of a sudden the car did a jerk (like bog feel) and the rpm did a slight drop and then continued up past 5k. This happened 3 times on the way home. Then today driving to work, I was coming along 4500 rpm and then the same thing happened but worse. Did the jerking until I let go of the throttle and the check engine light flickered on and off. Ok must have to do with fuel, right? Now let me give u some history. My car is in need of 120K service (new fuel filter is part of the service.) I added a chip to the ECU 2 months ago (no problems) and my ecu was just sitting on the passenger floor, not tied to the side, I did attached it back on on Sunday (could a wire or clip become lose?) Or I did change my fuel on Sunday. I have always used the same fuel for the last 8 yrs and on Sunday I used Union 76 the one WITHOUT MTBE. Could that be a cause? Being that my engine has adapted to the previous fuel? Any help much appreciated.