[1986c10]

My guess would be oxygen sensor or fuel filter. I had a bad egr valve and my symptoms were normal idle, off idle acceleration would lope really bad almost like blower surge and it would go away as it accelerated and if you let off it would make a weird sound then go back to normal idle. I found out it was the egr by unplugging the egr connection completeley, its on the passenger side of the intake manifold possibly touching the valvecover about in the middle, unplug it and if it runs normal its your egr but i suspect o2 sensor or fuel filter. good luck