Guys the ECO system is fixed!
I was busy at work and home for the past few weeks, finally got the time yesterday and went to Sultan Da Khu with my Mechanic. So we searched a few shops and finally found one chopped ECO System Vitz in a yard along with several other 1000 and 1300 cc chopped Vitz.
We started to negotiate with the owner and he started with 15,000 Rs and came down to 10,000 Rs inclusive of labour. So we got it changed and took it for a drive but the ECO system didnt started so we took a one week's warranty for the part from the owner and came back to Islamabad. Today when I went it, it came into action on the first traffic light. Right now my car is doing around 560 (without AC) locally in 37 litres of fuel, which translates to an average of 15. Next tank fill up will be yesterday so by the next few weeks I will be able to find out the increase in fuel average.
So lessons learnt, a bit of research on internet pays off, a bit of patience pays off, having a good mechanic is always a plus and a second opinion from authorized Toyota dealer is worthwhile but the most important thing is PW where we can share our experience and learn from each other.