Chevrolet: Emissions, 1994 geo prizm, high octane fuel

Question
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Followup To
Question -
I have a 1994 Geo Prizm and I can not pass our inspection because of the emissions test.  The hydrocarbons are twice the limit.  We have tried highest grade gas, pvc valve, gas treatment.  We have just put a new exhaust system on the car.  Any suggestions on what to do next?
Answer -
High HC is caused by a misfire. None of the things you did will cure a misfire. Check the condition of the plugs, wires, distributor cap and rotor, and coil.
Also switch back to an 87 octane gas.

We have been told it could be the oxygen sensor or catalytic converter.  From what you are saying we should try the plugs and gas suggestions first-is that correct?  We have the plugs here but have not put them on yet.  I do appreciate your input on this.  We have been going through this for 6 months

Answer
You could try the plugs first, but if you have been fighting this problem for six months, it is probably time that you take it somewhere and have it properly diagnosed.
About the gas, unless your car was made to run on high octane fuel you should not use it. It will not make the car run any better, it can make it worse, and it just costs you a lot more money.