If the code 34 is persistent you've got a wiring problem or the sensor or ECU has a physical defect. If it were just a boost leak you wouldn't see it until the engine had been run.
Have you made sure you've got spark when cranking?
Check for a signal on the STA input at the ECU while cranking.
I can't offer much in the way of specific information, the 1G never made it to the 'States' in any form and I don't know of any online resources for the 1G. This forum is largely US-centric (not by design), there is a UK specific Supra forum (mkiiisupra.net) where I'm sure you'll find more 1G-GTE owners and resources.
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