fuel injector, fuel pump on 1990 GMC 1500 Pickup

stalling or irratic idle, is this the fuel injector

This could be caused by many different things. You'll need to get it diagnosed to know what is causing the problem.
I have a 2000 GMC Sierra 1500 with intermittent high idle and had a diagnostics test performed. It showed nothing and was told process of elimination.
Changed Idler Air Control Valve as recomended by machanic and that didn't fix the problem