best to rebuild your bottom end first, i had a similer problem with a car before. it had a reciept for a rebuild & had only been run in but started to smoke, new turbo, fine for 6 months then smoking again, another (new)
turbo, 3 months, smoking again, another turbo,,,,,,,
2 months, smoking again........................

in the end i was ready to burn the car, so i left it up the drive for a while
& when in a better frame of mind i stripped the engine, the reciept was
for a complete rebuild, low comp pistons, shells, rings etc.....
(the work was done by Turbo Power Services in Leicster)
when i got it all apart, the pistons were standard with about 2mm skimmed
off the top, all the shells were odd (ie; genuine shell in rod,pattern shell in cap) standard size & had the bronze effect were they had done over 100k.
done over or what
Trading standards said we had a bombproof case, but Turbo Power Services had ceased trading

i think it must have had so much crank pressure & lack of oil pressure
that's what was causing the turbo's to blow.

anyway in the end i got a low miles engine (under 50k) and for peace of mind rebuilt it myself, never had a turbo problem with it since.