Sounds like turbo seals mate unfortunately i've been there and done this when i had my s2, changed the valve stem oil seals like you and still blue smoke,

I then took it to my local tuners and they said there should be no smoke almost straight after starting i then swapped my turbo with my mates while his rs was off road and no smoke with his turbo at all,

Have you got a good mate that could do the same for you to save you buying bits you may not need? hope this helps cheers and good luck, Grant