1993 Toyota T100 Question: Failed emmisions 93 T100

Low idle somtimes, rich gas smell from exhaust. I changed the spark plugs, oil change, air filter, new exhaust and tail pipe. Still failed! Check engine light comes on randomly. I have a rich mixture of gas. Is it the oxygen sensor? I have heard it may be the carb adjust or idle ajust. What do you think? Thanks T.Q. P.S. Here is the readings HC at 15 mph 100, HC at 25 mph 332, CO at 15 mph 1.50, CO at 25 1.57 They even failed me for fuel cap integrety! I'm going back to wyoming