Vacuum wierdness

[B6ayfour]

Alright guys so as i was driving the other day i looked at my boost gauge and it appears that when i let off the throttle about a second after it goes to full vacuum(normally around 22-23 inhg) it then leaps to about 17 inhg without me touching the throttle. this is random and most of the time the car will hold a solid 23 inhg at all times when off throttle. i just want to know if this is normal and if not what could be up?

Video of problem

[diagnosticator]

It is possible that the hose connecting the boost gauge to the intake manifold is collapsing at peak vacuum pressure, restricting the vacuum signal to the boost gauge. If this is happening, the collapse is most likely occurring at a weak point in the hose. What is the construction of the existing hose? Consider replacing the hose with a stronger reinforced hose. Vacuum rated hose will be very resistant to collapse.

This is assuming the boost gauge is a mechanical gauge, not an electrical gauge with a pressure/vacuum sending unit connected to the gauge with wires. If the gauge is the electrical type, then the sending unit is possibly faulty.

Besides the above, if there is a fault in one of the check valves or hoses in the engine vacuum plumbing, or in the crankcase ventilation plumbing, that could be the cause for the symptom.

If everything involved with the above hardware checks out then the intake cam timing adjuster hydraulic solenoid oil valve could possibly be leaking, allowing the intake cam timing to shift reducing overrun vacuum.

[B6ayfour]

It is a mechanical gauge so im thinking the weak vac lines that came with it are collapsing, also i have a crack in my valve cover breather hose, could that be causing it?
Lastly if it was the solenoid wouldnt it always happen? it can go days without happening then randomly it will.

[old guy]

I had a similar problem when I first installed my Podi mechanical boost gauge. It ended up being a pinched vacuum line where it made the bend in the steering column. I fixed it by adding a spring to the bend to keep it from collapsing.