A little update. After I drove the car for about 50 miles the check engine light came back. My friend explained me that after I disconnected the battery I didn't drive it long enough and that is why the check engine light never came back. Now the check engine light is on because the old error was stored in the memory and it need to be cleared. So, I purchased today actron cp 9575 autoscanner. After a scan I got p0171 and p0174 codes.
A code P0171 and P0174 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty.
There could be a vacuum leak downstream of the MAF sensor.
I made a reset and cleared all the codes that were stored. After that I tested and drove the car for a long distances. All's clear. The check engine never came back again.

Way to go!:thumbup:

Did you get the GT1 software?

It's still in transit from the other side of the pond. Once it arrives, I'll also need some time to get it working on an old laptop of mine. Lastly, I have a tendency to blow things up so please bear with me and I'll keep you posted.

So where did you end up ordering the sensor from ?

I purchased the scanner and sensor from Autozone.