I have also heard good results of using 1 gallon of denatured alcohol (or the highest proof 90%+ of rubbing alcohol) to 4 or 5 gallons of 87 oct gas will make just about anything pass. so at 1/8 to1/4 tank of gas add a gallon go get tested and then top off will gas to dilute the mixture.

Im gonna try it next time something of mine fails the smog test.

Also heard of ppl doing that and/or CRC's "guaranteed to pass" stuff.