Wont stay running for more than a few seconds and boost gauge going crazy
 

The other day I was going down the highway, I heard a high pitch but not very loud noise then I heard a pop. The engine started sputtering and died. Once I was pulled off the road I tried starting it again many times, it would start right up, run normal for about a second, rpm's would drop, the boost gauge needle would quickly jump from very low to very high boost, and then die. I also smell that it is running rich and it is blowing smoke out of the exhaust. I have replaced the plugs, fuel filter, and air filter. The problem has not gone away. Its a 2002 9-3 SE. Ive read many forums and cant quite get a thred that matches what i am experiencing with my car. PLEASE HELP!