Detroit 14L turbo,vpod,actuator issue. or a sensor

Hey all, I have this issue with my detroit series 60 14L.
Its 07 Freightliner.

When I drive and apply normal throttle, or even just have cruise control on set at lets say 55mph. The truck boosts up to 25-28 psi then goes down to 0-5psi then boosts up to 25+ psi again. And it just keeps doing that all day. Back and forth back and forth. When the boost drops you cant hear the turbo, but you can hear this squeaking noise. But if you apply more throttle it boost up right away.

Just replaced the EGR valve I though that was a problem. But did not solve it, went out for a test run bobtail. Same thing, cutting in and out.

The truck idles fine. Sounds like a jet engine. The actuator does not move up or down on idle. Its steady. When you start the motor and there is no air in the system. When air builds up the rod goes up and the fan switches off.
I was thinking maybe my actuator is leaking. But it would show on idle as well. Engine revs smooth except at 1500 there is a small hiccup I can feel it.
I'm trying to find out when I'm driving why is my boost go up and down. Even on a straight road no hills. Something cutting off the boost and then lets it boost up and cut off. And just keeps cycling like that. Getting like 5.5mpg and no power after 35mph.

 

So, here is a little update.
Changed turbo actuator it did have a small leak. But did not change much.
Put on a fuel gauge. Psi on idle is 23ish, but when I'm driving its falling close to 0. So I though it was my pump, replaced it. Nope. It must be the check valve behind the motor. Added a restriction to my return line. The psi went up.
Drove around still crappy. This truck deserves the name Freightshaker for sure. Shaking bad on idle, the cab vibrates even if I raise the RPM.
So, going to buy a new check valve install it.
Maybe I also need a new VPOD too. Anyway to test it? I just set up my laptop to connect to my truck. But gonna have to learn the program as I go. But I think there has to be some way to check a VPOD with comp before I spend another 300+ bucks.
Few more parts and I'm going to have everything changed around the motor. This is ridicules.

3 months ago I had Injector O-rings replaced. I hope they did not mess anything up there lol.
Also going to be installing new Cam shaft and Crankshaft sensors. The parts list keeps adding up.

 

OK, so here is another update:
1.Vpod changed. Same thing.
2.Crank, Camshaft sensors changed.
3. All sensors on intake manifold changed.
4. Turbo was new 40k miles ago.
Still doing the same thing lol. I spent the whole week changing parts from fuel pump to back preassure valve.
When I had the turbo off, I inspected it. no cracks chips on blades. no shaft play, no oil inside, VNT moved freely.

I have that sensor where it puts the truck in "boost mode" when I use this it helps a lot. The Squeal is much quieter and the boost does not completely fall.
If I put in the stock barometric sensor. The squeal is very loud. And on my boost gauge Psi goes to 25 psi and down to 5 psi and rinse and repeat when you drive.
I will post up a youtube video when I get a chance.

This weekend I'm going to check that valve by the intake manifold.
Its making me crazy.

 

Just changed the Delta P sensor. And cleaned the tubes when I had the turbo off.
Fuel pressure fixed.
I have now changed every single EGR item lol
So then I was thinking what would give the ECU a command to cut off boost. Turbo speed sensor.
So I unplugged the turbo speed sensor. Drove around and check engine light came on. But it looks like it did not cut off boost like it does with speed sensor plugged in. So tomorrow I will go buy a new turbo speed sensor and hopefully that will solve this issue.
If that will fix the issue I'm going to really pissed at shop that could not help me diagnose this. He hooked up the laptop, he told me no codes. And he is like" Oh Detroit does not really have any test to perform like the ISX Cummins"
What a joke.