I think i have mentioned this before but it could be your pistons, when i stripped the T230 engine i have down to a bare block 2 of the pistons had cracked between the rings, part of the piston between the rings fell out when i removed it and another chunk came off another when i took the rings off. The metal was black under the bits that fell out indicating that they had been like that a while and whilst the engine was running, the only symptoms this threw up was a little blue smoke as you have. Maybe get the RS pistons as a cheap fix they dont come up very often but you will need a very low milage block with little wear to fit used standard size pistons in a worn standard size bore. Personally i would never be comftable doing this. I cant read your PM im having problems with PF at the moment
I think the T series engines were ok in the short term but they all seem to be having similar problems now they are getting on a bit, standard zetec pistons do not like boost