Wow, great stuff. I just googled "2000 wrx check engine light flashes 4 slow 5 fast" and this thread is exactly what I needed.

Quick question for Rossco, you seem real familiar with Subaru factory info. Is there any recommended troubleshooting procedure for that pressure switching solenoid? Are there any known issues with a code 45... like is it probably that the solenoid is sticking or is it more likely an issue with the circuit? How does the ecu detect that fault?

I registered a profile on this forum because there's just so much more info available than any forum stateside. NASIOC has some info available for the gc8 swap, but nothing like this. This is great stuff.