I have the same issue, was “tuned” at 15psi when I purchased it, at first it was the actuator. Changed the actuator to a stock one and new battery cables. Changing the actuator dropped the psi (8) which was fine because it doesn’t have a lot of mods. It was happy for 6 months.
It started again so I put it into a ford workshop in feb, told them all the issues such as; cutting out at 4000rpm after not building boost properly making the car lose all acceleration and would shake its nuts off until I put my foot into it or turned it off. I didn’t care how much it cost As long as it’s fixed as it’s a very clean and tidy ute with an easy 130k kms on the clock.
Another actuator + solenoid, boost T and some piping Later and it again jumped up to 10psi and was going hard! Until a week ago and now it’s worse then before.
Throwing a wastegate code aswell as doing the throttle cut running 3.5psi which was the same after the first actuator.
im upgrading injectors, fuel pump, new turbo which is crap because it has no shaft play but apparently if the wastegates getting stuck you can’t really fix it??
Since changing the Coil packs and spark plugs Is when the issue started again.
gapped correctly and had 2 different mechs suss them out