Toyota Echo Automatic 2000 model. Stalls at low revs and shudders when taking off slowly. Replaced spark plugs fuel filter and air filter didnt seem to make any difference. Any ideas?

a repair manual will probably tell you. it has maintenance schedules, models of commonly replaced parts (spark plugs, oil type, weight etc)

http://www.papertownspdf.com/downloads/toyota-yaris-echo-repair-manual-1999-2010/

Sounds like an engine misfire.Does the check engine light come on or flash. If so, it may be a spark plug or ignition coil issue. The transmission can also cause a shudder problem. These transmissions are usually rather dependable though.

Have someone check your transmission fluid level. Probably low, so the shifting up and down is compromised.

a fuel filter can be a cause of power drainage, but it can also be many other things, start by replacing the fuel filter, and if its not that then work your way to your spark plugs and plug wires so on so on.. making sure you change your oil, oil filter, air filter, fuel filter, ignition rotor, plugs, and plug wires is a great idea to tune up and restore some power back

MISSING CAUSED BY MANY THINGS LIKE BAD SPARK PLUGS, WEAK IGNITION COILS.STOPPED UP FUEL FILTER OR FUEL INJECTORS.WEAK FUEL PUMP.CHECK FUEL PUMP PRESSURE SHOULD BE 44 - 50 PSI.LOW CYLINDER COMPRESSION CAUSE MISSING.

Possible, but it is for sure a fuel issue and must be checked starting from a choked fuel line, low fuel pressure at the pump or a bad blocked injector which improve on heat.
You will need to check the details of each to finalise the suspect.

My 97 Tarago did the same. Found it was a sensor near the air intake area, quite accessible under the passenger seat. It connects via a bulbuous screw in unit [valve]to the metal work of the engine with a tube to a small filter then connects to an electronic sensor. Unscrew the valve, disconnect from the sensor, and wash out the small hoses filter and valve with some fuel, Dry out reconnect and you will get your acceleration back. If anyone can help with the name of this unit, it would be easier to explain. Good Luck

change the mass air flow meter.

Try changing the fuel filter. Check the air filter. Check the timing. Check or change plugs and wires. Make sure there are no loose or broken vacuum lines under the hood. With the engine running, wiggle them all around and listen for a hissing sound.

sounds like the mass air flow sensor is malfuntioning, it is located on top of the air box.