.What Is My Turbo Actuator Doing?

[OhKarma]

TLDR: My fuel mileage went up when I put a new alternator on, but then I noticed my vgt actuator would "hang open"


12.15.25
Alternator failed and was replaced in Ohio and by the time I'd made it onto the highway I noticed my turbo sounded fuller, healthier even. The engine was quieter and for the 30 degree weather I was in plus going back and forth across i76 the fuel mileage was actually decent.

01.05.25
The truck had been sounding and running pretty good until the start of the day. From IL to MO, only 75 miles to stop for fuel, the truck sounded like it did pre new alternator. It was back to being a little louder but after shutting the truck off for fuel then the rest of the drive it was back to the new normal.

01.07.26
Unload/Reload in Ogden, UT
Again, the truck had been running and sounding great going out there, but after getting loaded and making my way back to the highway ending noise was a little louder and that's when I noticed boost pressure was 2-3psi lower for the engine load i was running at.
At 38% load boost is usually right at 8-9psi. This time it was hovering at 6-7psi.
At 60% engine, =50%tps where I try to limit input, I was seeing 14-15psi instead of 18-19psi.
But that only lasted for an hour because I blew a trailer tire and had to hit the rest area.

01.08.26
Now, the next morning after fixing the trailer I hooked up to CT but everything had gone back to normal while driving. It wasn't until later in the drive that I recorded full throttle pulls and after the long pull it was unmistakable that the actuator wasn't closing all the way after letting off and getting back down to normal driving speed.

At 40% throttle the actuator was at 7.5% and sometimes dropping as low as 4%.
At 60% load/Half throttle boost was sitting at 14-15psi and going no higher. It pretty much stayed "open" for the rest of the drive. No codes were showing after I shut down later that night. No CEL or anything. Started running the next morning and back to normal everything was.

01.12.26
Few days have passed and now I see that on full throttle pulls its as if the vgt actuator will get stuck open just a little and not close back to its usually position depending on how long the pull was. After multiple full throttle pulls it'll pretty much just stay open until I shut down for the day. Full mileage tanks hard trying to run at my normal speed when it isn't closing and making boost the way it should.
First run of today the actuator was wide open right after merging onto the highway and getting up to speed. I run at 58 and rpms @1350-60. It wasn't until I got up to about 1630 that realized that I had enough flow to get my fuel mileage to start going up. But that's like 68-69mph and I'd rather not be up there unless I need to pass and put space between someone.

Seems like turning the truck off for awhile resets it but now does that mean the actuator is going bad? Is my turbo sticking?
Anything helps