I SHOULD know where that line runs.....

i THINK its for the ac sensor thingy in the factory air box..If i was you is just pull off the vacuum line and plug the nipple on the throttle body. its almost pointless. that might be your issue. i plugged mine when i ripped out my air box and put in one of them oldschool chrome round filters.

im still not familiar with everything on the engine.......factory air box?

The round box that the air filter goes in. if you remove the lid you'll see a little green thing in it that vac line runs to that system, which apparently helps with cold starts. its nothing important to have and its something ive removed on all my s10s when i went with aftermarket air set ups. Just pull off that vacuum line from the throttle body and pull the rubber nipple off the line,then plug that nipple with a screw or something tight and plug the port on the throttle body.

Any updates on this?