Thanks for advice thus far.... New spark plugs to go in on weekend (not just for mystery smoke but for stuttering miss as well!)
Also, BlakeNZ what did you do to re-con your turbos? I've heard whisperings about upgrades (steel impellers? oversize impellers?) or can you get new seals and bearings in a kit from Toyota? I guess I'd like to increase the boost at some stage so I'll need to ensure turbos are in good nick beforehand.