1998 Isuzu Amigo jerking and or stalling while driving.

I bought my Isuzu Amigo a little over a year ago. It doesnt want to start alot of the time and when I am driving it likes to jerk like its stalling out. When I stop at a stop sign it tends to stall out and die if the gas is not pressed. It usually starts the stalling at around 2500 RPMs. Sometimes it seems like it is not getting gas to it even when I am pushing the pedal. We have replaced the fuel filter and fuel pump along with the spark plugs and wires. The check engine light and ABS lights stay on constantly. The jerking only occurs when the gas is pressed, it doesnt happen when the car is idleing.