???sensor in charge tube?????

That is not a sensor. That is the Pitot jet. It is used for fine tuning your jetting for altitude or temperature changes. It basically bleeds off boost that charges your fuel bowls. The larger the jet, the leaner your sled should run because of less float bowl pressure. I think I have all of this right.LOL

As for your gauge, I have mine plumbed the same way. There is a hose barb facing the carbs in the center of the intercooler. There is a small tube running to the gauge. My gauge doesn't jump around much at all. I have a Pro-comp silver face gauge. Make sure all of your hoses are sealed well and not leaking.

Hope this helps.

Lance

For your gauge bouncing iv never seen a boost gauge do that but on my fuel pressure gauges i always put a needle valve in right before the gauge and just barely crack it so your controlling volume maybe something to try

Take a picture of the sensor so we can figure this out. I have nothing extra on mine.