Well i do not know what is the plug number. All i know is that i bought DENSO Iridiums.
You know the weather of Islamabad is chilled even now, the car is with me from last 3 weeks, so i never turned on the AC.
I am calculating by turning the TRIP A to ZERO while i am filling my fuel tank and then i divide the total mileage with the litres i fill. Just the way you told me.
Frist line drops around 76, Second drops around 41 and so on. So its not going above 440 Km in 36 litres of Fuel (in which 8 Litre is HI-Ocataine)
440 Km with my driving style is very with very light foot, on the roads of Islamabad at Night (Without AC), when there is no traffic is very less.
Pakistani assembled 1.3 Corolla is giving me more than that 
Now i was told that CAT should be removed it might be cloged or something, no one told me even the mechanic that there is another CAT :@
Trust me dude, if this car gives me in Islamabad city 13.88 With AC, i dont want anything more than that. But the fact is that my driving is style is very calm and its just like Highway and its not giving me more than 11.4 Without AC. 
And i press Gas pedal like 10 %. I mean if any one sitting in the car, wont even listen the GENERATOR type sound of new VITZ if the windows are closed. Lols
And my Tire is not stock profile, my tire size is 185/70/14. This tire is 20mm wider than Stock tire. (I asked many tire sellers, they said if you are looking for fuel average then it has nothing to do with the tire which is 20 mm wider.)
So basically i am stucked, dont know what to do.
Because the day i ON my AC in summer my average will drop 2 KM per litre. and it will be 9 km/L.
Anyone having new Vitz will start hating Vitz with that kind of average 
So anyone on Pakwheels, who got Vitz 2008, 1.0 Assist me what to do.
Thanks.