id say boost leak as when my bosst pipen had poped off i couldn get 8psi with no jubilee clip ( fook knows what the turbo was producing though )

that or the turbo is fooked, not unusual if its been running with a boost leek before and then it decided to go bollox


take it to another tuner as 8psi is not alot for a turbo that size , surely it can flow more air UNLESS ya boost hoses are the size or toilet waste pipes