[submariner409]

The plugs should be ACDelco #41-987 Professonal Platinum with the gap checked at .050". The coil boots should be checked for cleanliness and spring (internal connector) tension. The coil cassette ICM connectors and ground spring should be checked for cleanliness and proper contact. Make sure the PCV connections are secure. make sure the injector connectors are secure.

You do not need any external scanners or computers: it's already built into the car. Read the thread at the top of the Cadillac Technical Discussion page, Technical Tips, "How to pull codes on later................". learn to pull your codes and don't clear them - keep a log. If you clear codes within a few weeks of an emissions test the car will fail until the system resets to a "Ready" status.

Don't ask why the Northstars dislike anything other than AC plugs. It's black magic, but well documented in here.