Bought A New Talon

i just bought a new talon a 92, well new to me old to everyone else, no rust 80K miles and a shot tranny.. was wondering i start the engine and it idles rough at anything below 1500 above that it runs smooth as hell... idle likes to fluchuate engine light was on tryed to get codes, maybe code 14, 24, or 34 one of them. cleared the codes *disconnecting batt* and now no engine light, i noticed when i grab the aftermarted o2 sensor the enngine starts to die, if i leave it alone it runs fine. maybe a vacuume leak? HELP ME!

do the normal checks. vacuum leak test, compression test, check and/or replace plugs and wires, stuff like that.