I have a 2000 Chevy impala LS and it does two different things where i have to go by to figure out whats wrong with it. First, the car starts up fine but if i don't give the engine a little rev then the rpm's will start to jump up and down and the engine starts to choke out and eventually stall out after about 10 seconds of doing this. Second, car runs fine for the first 5 minutes but after it warms up car seems to have very poor acceleration power, example, driving with gas pedal half way down the rpm's will reach about 2,000-2,500 then all of a sudden just drop back down to 1,000. Basically unless i have the gas pedal full throttle, the car doesn't hold its rpms. I have so far changed the spark plugs, spark plug wires, fuel filter, electric fuel pump, catalytic converter, got the leak in the exhaust pipe fixed, tried spraying the throttle body with cleaner and got the fuel injectors cleaned. The check engine light use to come on and say cylinder misfire but after i did all this work it has not misfired ever again but still has the same problems of choking out and not holding rpm's. I'm not a mechanic but does anyone have any clue as to what is wrong with my car? thanks

I hope you can help me, I have a little problem with my 2000 Impala there is a little shudder when I run from a complete stop then at 3 gear feels like another little shuddering, 3 weeks ago there was a code P0102 and I change the MAF. Before changing the MAF feels a little instability in the engine I open the hood and the engines shudder a little and there is a little variation too. After the MAF replace I believe the problem will be fixed but don�t. I get to the service and they clean the PCM after that I believe the problem will last but don�t I receive a recall 2 year ago for Fuel pressure regulator, Can you help me with this problem.

Thanks.

Frank Esquivel.