95 S10 surging at low speed/part throttle

[JScottB]

I have a 95 S10 2WD, 4.3 with 5 speed man trans. When idling, the idle speed will jump up maybe 300 rpm then come back down. It also seems to surge at part throttle or at low speeds such as driving in town and is most evident when the engines cold but it's still there when it's warmed up. I recently did a complete tune up such as plugs, wires, cap, rotor, pcv valve and new ign coil which solved a previous problem. The check engine light isn't coming on and a recent computer scan done by a local auto part store showed all was well. I just replaced the throttle position sensor which helped but only a bit and I've also cleaned both the AIC motor and EGR valve, both of which seem relatively clean in the first place. I'm trying to avoid a wild goose chase on this so do any of you have an idea of what's going on and how I should test it?