2000 Toyota Echo...how do you replace the air filter?

Have you checked the injectors to see if any are leaking ?

A 2001 echo a tune up , you will need sparkplugs , air filter , pcv valve and i would put some injector cleaner in the tank to help clean the fuel system, this cars fuel filter is inside the gas tank and is good for the life of the fuel pump and doesnt need replacing at this time,. take note that alot of the newwer toyotas use iridium sparkplugs, you will see a notice under the hood on a small sticker its sometimes located on valve cover or on radiator post warning you to use iridium plugs. i hope this helps, good day.

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

Did you ever get this resolved? I have the same issue with our 2000 Toyota Echo.

I also have a Echo and would suggest:
Air filter, spark plugs. If it is still sluggish I would then replace the upstream 02 sensor. The fuel filter is apparently lifetime so it should be okay.

Sounds like a fuel problem. Check fuel pump and fuel rail. Do a fuel line pressure test. Try cleaning inside of throttle body really good and also the TPS at that location. There's many things that can make a car run bad. 

They face down into the air cleaner box.

A P0171 code does not indicate a vacuum leak; it indicates a dirty mass air flow sensor. This device is located between the air filter box and the intake manifold. Locate it, unplug the wire harness, and remove the 2 screws that holds it onto the intake pipe. Look down inside th sensor, you will see 2 small wires, that are probably covered with fuzzy things...using a spray cleaner, such as brake cleaner, spray the 2 wires until they are clean and shiny. Do NOT use compressed air, that will damage the sensor. When it is clean; reinstall it and drive it. The computer will recognize the now clean sensor, and your troubles will be over.

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

http://www.carspace.com/guides/Changing-Cabin-Filter-on-Toyota-RAV4-Echo-Scion-xA-and-Scion-xB