Just out of curiosity can anyone tell me when Delphi Products were first used on Blazers or GM vehicles in general. Thanks.

 

This what I found. Although PettyFog can probably give you more in-depth info...
History:

1888: Delphi Auto's earliest predecessor is founded.
1991: GM organizes parts holdings into Automotive Components Group.
1992: J.T. Battenberg, III, takes the helm at ACG.
1995: ACG is renamed Delphi Automotive.
1996: Delphi institutes lean manufacturing practices.
1997: GM's Delco Electronics is transferred to Delphi.
1999: Delphi is spun off from GM.