91 s15 jimmy 4.3 rough idle

[wlf89]

i have gave it a complete tune up plugs,wires,cap,rotor. i cleaned the egr valve not as bad as i was expecting it to be. i replaced the iac valve few months back and that helped alot but it still idles rough has died a couple of times but not usually just a inconsistent idle. other day while tinkering with it i cranked it up with the air cleaner assembly off and it was running smooth as has in a long time , but when putting it back on and hooking the vacumm line up going from it to the throttle body it lowered rpms and started idling rough again. that line goes to a sensor on the inside of the air cleaner (thermal air temp sensor i think)? do yall think that could be my problem or likely something else? that sensor is $60 so hate to buy it if not needed. also doesnt ever throw a check engine light. also noticed looked like the oil pressure sender is leaking oil around the plug connection but dont think that could have nothing to do with it could it?