Leathermang,
Where is the expansion valve? I don't see it? From the Performance Products Catalogue the part looks fairly small with screwed threads on one end and flange attachement at the other end. Perhaps it fastens to the evaporator and to a hose? It would be nice to figure out a way to flush right through the evaporator, without having openings inside the passenger compartment. (sounds like a potential mess or major surgery in taking everything apart??)