If your oil pickup pipe is blocked no oil can get to the turbo which in the end means a sneezed engine
The fact that it only happens at 4k would tell me that its half blocked defo check that pipe and change it its an easy job.
* go to VW buy oil pickup pipe, 5l of 5w 40 oil, oil filter, sump plug and sump sealant this will set you back £62.86 (did all mine last week)
* drain your oil and wip off your sump.
* onbolt you oil pickup pipe and put new one on.
* clean your sump and take off any old sealant.
* re-apply your new sealant and bolt on your sump. (Don't be scared to use a lot of sealant)
* leave the sealant to set I left mine overnight.
* take off your old oil filter and replace with new one remembering to half fill the oil filter with fresh oil and rub fresh oil around the seal to create a good seal when you tighten it up.
* add your new oil remember to unplug the dip stick to avoid any air locks..
Hopefully this will sort your problem.
