I have one but I couldn't figure out how to use it.

If I hold the button on the left, it shows "A", if I hold it again it shows "B"

For the right buttin, it shows "HI" then if i do it again, it shows "LO" and for the 3rd time I think it shows "OFF"

If I hold both buttons, it shows "A55" and when i press the button on the left the number decreases (like 54, 53, 52, 51...) . right button makes the number increase (like A56, A57)

What does "A" and "B" mean??? also why can't i set the boost with psi? What does that 55, 56, 57 mean??

 

You NEED to find the instruction manual for this thing. You're just guessing w/o it.

But just as a guess from your post, it seems to have two boost seetings Hi and Low. Push right button to select which is active. Press both buttons to show current boost setpoint. I guess 55,56,57 is psi (but it could be other units, like metric). Pressing and holding the A button decreases the current boost setting, while pressing and holding the B button increases boost setting.

RTFM. I would not take the chance of blowing your engine just because you are unwilling to read a manual. It should be a free download from AEM's website.

 

Hey Burak! check this thread over at AEM.

How to set up the Tru-Boost controller

 

I have one. It's interesting to setup. You don't dial in a boost, you dial in a duty cycle and a few other parameters.

Tim