heres the tsrm for isc
http://www.cygnusx1.net/Supra/Librar...spx?S=FI&P=106
and this one is for the air induction system.
http://www.cygnusx1.net/Supra/Librar...aspx?S=FI&P=94
are you sucking in un-metered air between the afm and throttle body? that would cause shit idle. seen you said you checked all the way up and down the induction system tho..
id check the resistance for the isc. might be a chance that even if purchased new.....