Smog failed

My 1986 toyota pick up failed smog in Sacramento, CA. Specifically it failed the HC test Max allowed at 15 mpg is 146 and my truck came in at 340! What could be the specific reasons for this? My truck is now a gross polluter. Last night I replaced my spark plugs and it does sound better, but I am not sure I will pass smog yet. The high HC concerns me, mostly because I dont know what "controlls them"
could it be when they did the test they had it in the wrong gear? Could it just need a tune up?

thanks!