By way of follow-up I got it to pass with flying colors last weekend. Although I replaced the O2 sensor and plugs, dist cap and rotor the culprit was actually poor timing. Like I said earlier I just bought this truck so didn't know much about it but the distributor lock bolt was a little loose and the distributor was slowly drifting to more retarded timing. When I put the light on it the reading was about 1 degree before TDC (really surprised it ran as well as it did)....so when I reset to about 12 before per spec it ran better and cut the emissions by 1/3 for the CO. I know you mentioned too much advance would affect CO negatively and that may be right but this was so far retarded that it just waa not cleanly and completely burning the fuel.

Anyway, the good thing about AZ emissions is you can use the first test as a diagnostic (for the $28 fee) since you get one free retest! :-)

Randy