GM light truck "W" code engines are all CPI. There are variations such as CMFI and CSFI, but all are CPI systems.
http://service.gm.com/dealerworld/vincards/
There is a GM TSB, (00-06-04-003B) that deals with retro fitting a CSFI system back to a CMFI system.
Fuel pressure specs for all "W" engines: cold engine, pump running, engine off: 60 to 66psi.
Leakdown: Not to drop below 55psi after 3 to 5 minutes.