your best option would be to just rebuild your turbo.
and a simple compression test will tell you if you need a HG or not:
http://www.cygnusx1.net/Supra/Librar...ection=EM&P=20
this question has popped up alot latly for me so make sure to read the part that says :
minimum pressure:128PSI with 14 PSI differance between cylinders...
i believe its water cooled, and oil lubricated...
http://www.cygnusx1.net/Supra/Librar...Section=TC&P=2