Thanks for the replies...
Anyway, for the benefit of others:
- The bottle of injector cleaner did nothing.
- I reset the Ecu by disconnecting negative battery cable for half an hour. It went worst! Start to show 0 consumption under 1200 rpms! Meaning that with engine on is almost always burning fuel!! Throttle, or no throttle!
- So, take it to dealership to clean eletronic throttle body, that was very dirty by the way, and after the cleaning it needed some TPS and idle calibration with HDS (Honda software) connected by the OBDII...
Success!!
Now it shows zero consumption from under 2.5k rpm... But will test higher to see upper limit... Also the engine is now smoother and refined... SGII was reading right...
My guess was right, a dirty throttle body don't completely close letting some air pass it, and the ecu compensate it by burning some extra fuel....
It's a preventive maintenance worth doing, because not only can improve gas milleage, as it prevents a faulty throttle body with excess of carbon on it, and I tell you: electronic throttle body AIN'T CHEAP!
Cost me an hour labour...