having the same problem in my customers sts 370z , we tried everything to make it boost again we even made a direct hose form the turbo to the wastegate so it can give the maximum psi of the turbo and it gave 3psi , no leaks , we made a smoke test , their was a history of a bad pcv valve which made oil come out from the exhaust ,went all the way to the intercooler,maf sensors, piping etc etc , fixed that and cleaned everything and still doesnt build boost , check engine comes back on and idle at 1100 , spoke for ben STS went step by step with a confrence call with my mechanic and it looks like the 3 port solenoid is messed up since we made a and its suppose to make a ticking noise and its not , this is the last solution if not then its a bad turbo which went bad after 1000 miles or so , although their is no smoke,shaft play or anything , so lets see what happens after changing the 3port solenoid . wish you the best .
p.s all of this took place after loads of exhaust leaks that happened and fixed them then changed tha bad place of the boost controller which was under the back bumper . since then problem after problem has been happening .