What is the stock boost of the Evo X?
What is the max boost with 91 octane?

I've seen stock numbers range from 21 tot 23 psi.

Run up to 24, you should be fine

Dan he is running on 91 octane so i would keep it stock boost until he gets tuned.
We got lucky with the 93. I recently learned the Evo's in the US is tuned for California standards, so that is why we can get a way with some boost raise safely ... :)

I didn't realize he said 91.

:(

yeah i get 93 and run 26 psi

What kind of knocking tells you that your boost is too high?
In 4000Rpm? 6000rpm? I heard little knock shortly when I stomp the accelerator. Is it normal? Or maybe it's not knocking but other sound.
When is knocking mostly occur, day or night? I'm living at 100ft elevation (sea level)

if you hear knocking.. stop reving the C##p out of it and turn the boost down. You will damage your engine if you continue to drive with knock.

Knock or pinging means that you are getting pockets of mixture (Air/Fuel) are igniting out of sequence and not to the intended timing of your sparkplug ignition.
Knocking sounds like a metalic pinging sound. if you hear it you are running too lean and are out of sequence - get it looked at and dial your boost back.