Sorry to hear about your boost problems, I've had a couple myself and for fault finding I myself found it easier to connect a compressor or something else with 1,1 bar to the feed of the vacuum lines. That way you can at least test the sequential valves and solenoids with a 12V source and see how and if they work and if there is a leak in those lines. Hope this makes any sense and helps. For understanding the system, I find the faq here very helpfull, or http://www.max-boost.co.uk/max-boost/supra/boosting_the_beast.htm
Btw, what happens in TTC?