If u ask me ur just burning up the oil thats being sucked in through the pcv.. thats y it happens on idle, if ur not smoking on boost or overrun i would rule out the turbo... sounds more like when u cleaned the idle valve etc u dislogged some oil from ur plenum & its slowly slowly burning up
i wouldnt really worry unless it increases drastically, then i would consider checking the valve seals.. if the turbo is a good one i really wouldnt bother.. alot of ppl just blame the turbo instantly without checking other problems..
kon