To be honest, a standard of 150 ppm is a pretty low standard. I've seen vehicles fail with 900 ppm before. Anyway, a hydrocarbon is unburned fuel. 90% of all reasons you'll have high hydrocarbons is a problem with the ignition system. Plugs, wires, cap + rotor will likely fix it. There are some other things that could cause it. Also, adjusting your ignition timing will help a lot also. Retard the timing a little bit, and you'll lose a little bit of pep, but gain a lot in the emissions area. Turn the distributor counter clockwise just a little to retard the timing.
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