320km per tank economy

[R3DN1NJ4]

Hello all,

I'm trying to find the reason of such a bad fuel economy in my 2008 yaris sedan, AT,1.5 L, 105000 km.

That should be around 18-19 mpg...

i have:
* cleaned throttle body
* cleaned MAF sensor
* cleaned PCV valve and hose (had lots of gunk and was stuck, it now rattles a lot when shaken)
* changed ATF
* changed spark plugs (NGK BKR5EIX)
* checked drum brakes
* checked for error codes with OBDII and torque app.
* checked coolant temp (averages 85 °C / 184 °F)

The car is really responsive, speeds up fast, starts like new.

i have also a couple questions.

01. Does yaris have an EGR valve?
02. How to check o2 sensor? can i test with multimeter ?
03. What else could be the culprit? Catalytic converter? fuel injectors? coils?
04. Where can I find sensor reading threshold to compare ?

thanks


UPDATES:

07/12/14 - Changed B1S2 O2 Sensor.
07/23/14 - Cleaned spark plug well (had oil) scanned B1S2 voltage, still 0v.
07/25/14 - Changed valve cover gasket and spark plugs for Denso SK16R11.