S80 T6 2000, codes

[MWaals]

Goodday everyone,

I drive a S80 T6, 118000 kms on the odometer at the moment, transmission replaced by Volvo dealer at 105000kms,
bought it used at 113000 kms.
The engine light at the right side of the dashboard lit up with the well known
message 'Emisssion Service Required'. So I hooked it up to a computer and it gave me the follwing codes:

ECM-6805: Turbocharger (TC) Control Valve
Condition: Reduced Boost Pressure

ECM-272A: Adaptive lambda control,
bank 2. ECM 271A Long-term fuel trim, bank 2, Lower

So I changed the TCV with a new one and also the front o2 sensors were changed.
And 1 coil was also replaced, because the car started sputtering and the engine light started to flash.

So the car was reset and the codes, message and the engine light that lit up were gone.

Then after driving for about 250 kilometers, the message came back on and the light lit up again.
So connected it to the computer, and i gave the exact same trouble codes again.

What could be the problem? Everything in the cars works, I don't notice anything wrong while
driving it. It pulls hard and it does not hesitate on accelerating or anything.

I hope someone could be of any help, I would truely appreciate it.

Thank you for your time.

Mark Waals