losing boost -> something electronic?

[indeck]

in a nutshell, i get the full 10psi when i first start driving the car, after anythign between 30 seconds and 20 minutes the car reverts to 7psi and stays there. If i shut the car down for 20 seconds im back to 10psi again.

std ecu, exhaust, fmic and not much else.

i'm at a bit of a loss and can only put it down to sometihng electronic? can the standard ecu reduce the boost?