2003 Impala 3.4. 159k. Catalytic converter replaced today. Mechanic scanned but no codes at all. Car runs much better and smoother but still slight jerk between 20-25 mph after 1/4 on temp gauge. Mechanic said O2 sensors are fine. The car still stops jerking when I unplug EGR. All the openings are clean into manifold and EGR line is clear and in good shape, wiring is good also. I have replaced TPS sensor, EGR valve, crankshaft position sensors, cat, trans fluid and filter change. I cleaned the MAF sensor with MAF cleaner and the wires look perfect. One was black with soot when I cleaned it but now it is shiny (I did not touch the wires at all, just sprayed with MAF cleaner). After I got home from CAT replacement I unplugged the MAF harness while the EGR was plugged in and the jerking went away also. Could the MAF be bad without throwing a codde, and could it cause the slight jerk between 20-25? The idle changes (lower) when I unplug the MAF sensor. I appreciate any info as the car is getting in my head at this point.