Had this exact issue over the past week, about 500 miles after having my X48R fitted.
Absolute pain, went from feeling like the throttle was sticking a little bit to juddering violently, like a learner driver mashing the throttle on and off in 1st gear.
Got to the point where it was dying after running from anywhere from 20 seconds to a minute.
I'd had a Forge recirc valve fitted with the turbo, first code that came up was this -
P0039 :73 - Actuator stuck closed
Took the recirc off, valve inside was a bit sticky but looked alright to me, sent it back to the tuner who checked, pressure tested and re-greased it, valve was all good.
Put it back on the car, same issue and code...
Got my stock valve posted back to me and put it on the car.
Seemed fine for a few minutes, then the juddering and rough running came back.
After a few minutes attempting to get the car back home, it went into a sort of limp mode, spanner came up and it ran a lot better!
Felt like it had about 50hp but at least I could actually drive it.
Checked the codes and had this -
P00CF :62 - Signal compare failure
Did a pull on the way back and it had mad turbo flutter which sounded cool but clearly showed the bov was doing sod all -
video
The chance of both valves dying is about 0%, so
must be an electrical issue.
Back under the car we went
Spent a good while checking all the wires going to the valve actuator, no visible issues.
What solved it for me was a £7 can of WD contact cleaner, plug onto the valve didn't look too bad but it was a bit dusty, gave both sides of the connector a good few couple of long sprays.
My tuner also told me to check the sensor plug on the coldside boost pipe just behind the bumper on the gearbox side, believe it's post intercooler.
That one was really really gunky, gave it a good cleanout.
Plugged them back in, cleared the codes and the car is back running perfectly!
I can only assume the issue has showed up now as the plug for the valve had been unplugged and replugged as it had a new valve, same for the boost pipes as I had bigger pipes installed - and they didn't quite contact the pins correctly.
Best of luck fixing yours