1992 Chevy Blazer Ideling Problem

I had a Lumina that had a lower intake leak causing a vacuum leak. It would idle up then down then up. Ect

Sometimes you can locate a vacuum leak by spraying carb clean arount the engine bay. Be carful though and DO NOT spray to close to the coil, plug wires, ect. The idea is that the engine is sucking air someplace and so will suck in the carb clean and either rev up(most likely) or it will cause it to stall.

I would spay around all Vacuum lines and your intake. This really sounds like a Vacuume problem.