Start with checking for error codes and testing the AFM and the ECU coolant temp sensor. When did you last check your spark plugs? Check the plugs for signs of fouling and to see if oil is getting in around them and the wires from a leaking valve cover.
http://www.cygnusx1.net/Supra/TechTi...ror_codes.aspx
http://www.cygnusx1.net/Supra/Librar....aspx?S=FI&P=1
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