I just bought a truck with the O2 sensor unplugged? No cat? idles too low?

[naviblueflame]

Hey I just bought a 1995 Chevy Silverado with the TBI 350. The backyard mechanic that owned it before me put a different motor in it since the first one burned 6 quarts of oil on an hour trip...tailgate was black... but he replaced that one and now my Dad and I found that after warming up the motor in it now idles too low and dies at stoplights...we replaced the spark plugs with ACDelcos and that helped but it still dies..we also found that the O2 Sensor's plug is just hanging and not plugged in...We looked for the plug in but couldn't find it..I also noticed that it has dual exhaust with no catalytic converters..so with the two O2 sensors did they take off the first O2 sensor before the cats because it'd throw off the fuel air mixture even more than not having the first O2 Sensor? We're gonna try to find the first O2 sensors wire anyways tho, it could be tucked away in the wiring harness..and after we get teh O2 sensor plugged back in then we'll time it with a timing light.. any suggestions?? Thanks!