I stumbled upon this today. While tinkering with a old TBI I discovered that you can adjust the idle. On the front of the base look to the right (pass side) you can see a very small expantion plug just below the sticker. Use a small punch and knock that plug out and you will see a torx head screw. Just turn that screw clock wise to idle up and counter clock wise to idle down.
92 S-10 Blazer 4x4 Vortec 4.3
85 S-15 Pickup 4x4 2.5 iron duke