Please Help! No power after 7.4 lbs of boost ...
 

I was racing a RX-8 on my way home at Friday night. After hitting 4th gear, he's bearly see in my rear view mirror. Then I hit 5th with boost still on. I heard a pop sound coming from the front and alot of backfire from the rear. After then, each and everytime I reach to 7.4 lbs or 0.5 bar in boost gauge, the car doesn't have any power and alot of backfire in the back. It feels like an air leak. I checked all visible vaccuums and IC pipes under the hood and nothing seems to be loose. The car feel normal before 7.4 lbs of boost and on regular driving, but it's just when I boost it up til 7.4 lbs, things start to go negative after that. Can someone please help me ...

*** Did a search, but nothing seems related. The car is very normal and full power before 7.4 lbs of boost. And if I don't boost it at all, everything seems fine. It's just that once I boost it over 7.4 lbs, problems start.