This is a final chapter to a series of posts I had made to this forum regarding intermittent boost pressure issues in my '97 850R. My mechanic and I "dug our heals in" this morning and finally figured out the issue.

There is a presure/vacuum valve that is attached to the outside of the air filter box (not sure exactly what it is called). This valve has 3 small hoses on one side and a sensor on the other. From this valve, one hose runs to the air intake hose, one runs to the waste gate actuator and the third runs to the turbocharger. Each of these points are color coded on the valve, so as not to be confused. Well, somebody got it wrong and had these hoses going every which way. I had the ABS repaired a while back. The mechanic that had it apart then, was the one who likely messed this up.

This caused a 3-4 MPG reduction in gas mileage and unpredictable throttle response. It also threw OBD-II codes for boost pressure.