I used vacuum line to install my boost gauge, an autometer sport comp, and most of the time it works fine.

However after awhile it only reads vacuum and not boost. I know it's boosting because i can feel it and i can hear the turbo spool, but the gauge doesn't register.

I t'd off the line that goes from the end of the silver fuel rail where the fpr is. That is correct right? I would think so because the gauge does work a lot of the time, just not always.

1. Move the vaccum line to the line that goes from the FPS (fuel pressure solenoid) to the intake manifold.
2. Look for kinks of the vaccum line (which give you bad readings from time to time)...