Erratic Boost gauge

[BoostBoy]

So the pic below shows how my vacuum lines have been setup...the boost gauge needle is erratic when boost kicks in....is this because it is on the same line as the boost controller valve? Where should I move it?

[oldcorollas]

yes, your boost gauge is showing the pressure going to the wastegate.

either move it to a dedicated line on the plenum, or, Tee'd into the fuel reg/ECU line (i prefer seperate lines for them too tho )