I have 06 g35 6MT
The best fuel in my country is causing my car detonation?
Any suggestion, I think I have to use octane booster?

A can of octane boost only gives you a small .x octane boost. Hardly worth it.

If you are desperate for an increase in the octane rating of your fuel, you can try to find Toluene or Xylene by the gallon at hardware shops and mix it with your gas.

As a general rule

(octane rating of your purchased gas) x (gallons) + (114) x (gallons of toluene or xylene) = A

A / total gallons = new octane rating

for example: you have really cheap and crappy gas = octane rating = 85
and you want 20 gallons of good gas = octane rating = 91

(85) x (16 gallons) + (114) x (4) = 1816 / 20 = 90.8 which is pretty close to 91.

Simple algebra can get you the ratios for other situations. As a note, Toluene and Xylene are pretty expensive so I wouldn't really resort to this unless my car was borderline undrivable. Also make sure your potential additives are very pure.

Are you sure its the gas causing it and not something else?

Did you do any kind of service recently?

I have been 2 times checking my car in dignostic manner to find out is my car comp. having somekind faults. Turns out everything is ok.

Did they replace the ECU?