HOLD THE PHONE!!!
I encountered the SAME PROBLEM only to have EVERYONE tell me my turbos were bad (seals,etc.) and this guy on Toyota newsgroup suggested I FIRST TRY a $1.87 PCV valve since crankcase ventilation is VERY CRITICAL to the Supra.... I tried this (starting with cheapest fix first) and it WORKED!!! No smoke or anything since... I knew my turbos were not BAD as everyone had indicated because I hardly ever get on them and run 15-17 PSI when I do with turbo timer and all... So, PLEASE, before you've written off turbo seals, etc, try the PCV valve replacement available at any local auto parts store and that may be the cheapest fix you'll ever find... Of course, everyone's problems vary, but this cured mine and for all of 10 min. of my time and $1.87!! Try it and let me know!!!