0.6 bar boost
 

my car is JDM sti, the highest boost is 1.5 peak then 1.2 steady. last night I kept 200 km/h and high rpm. after a 1? mins., the boost can't over 0.6 bar. I can't find any problem and no engine light on. Then I stopped for 15 mins. After that, it became normal again. I have checked if there is a code, but nothing to be found.
What is the problem??

New age or classic JDM STi?
If its a new age then I suspect it has picked up det and reduced the multiplier right back so your pushing no boost, if its a classic its definately in limp mode.
Try an ecu reset on the classic, the new age is a little more complex, get the spanner out and disconect the battery and leave it for a couple of hours :)

Tony:)

It is a new age sti. I have a ecu delta dash but read no error code. What is the meaning of "it has picked up det and reduced the multiplier right"?
Thank you

The ecu has a multiplier (x16) which controls (afaik) the ammount it retards, if it picks up det then it will knock the ecu back reducing boost until it figures out the problem has gone (it can take some time).
Normally your multiplier runs at 16, it will reduce to say 12 as an example if it picks up any problems, this will in turn reduce your power.
Disconnect battery and leave for some time ;)

Tony:)

Thank you very much.