Think you have several places to look at:-
EGR - I've heard EGR stuck open can cause this ..so dismantle and clean service EGR could be a solution - check motor is operating the EGR -- needs forscan, EGR is an item that needs regular attention, is a service item, as it becomes carboned up .
DPF - a blocked or partially blocked DPF will not allow the engine to breath - forscan will tell you how much percentage DPF is blocked.
TURBO ACTUATOR - this is a vacuum or pressure operated device that opens the turbo waistgate to relieve pressure or create boost, if it is malfunctioning:-
IT could be the diaphragm in the device has holes.
OR - the rubber tube connected to to the pressure vac source is - perished split or fallen off.
OR -the shaft that turns the valve has become disconnected ..or has corroded.
MAP faulty and giving the wrong info this is in the top lid of the air filter - can be cleaned.
BOOST PIPES - splits, holes or badly sealed at joints.
TURBO - could be damaged or worn out ..or seized -- take large air filter rubber hose off the [check that turbo is free spinning with finger -engine turned off] [check no damage to vanes] [check no pool of oil]
CRACKED MANIFOLD to which the turbo is attached.
BLOCKED AIR FILTER FORSCAN - Here they recommend Forscan.
NOTE: you can use Forscan to get correct fault codes with proper explanation of them - a generic fault code reader may be somewhat misleading.
"Forscan" is FREE software that you download to a laptop..you buy the interface cable (of which you pointed out on ebay -- this is just the cable you need a laptop)
You can join the Forscan forum ..again free, to get the software and more answers.
https://forscan.org/forum/all the best.mark