1987 Ford F-250 wont pass smog check

1987 Ford F-250 mileage: 150,000. I live in Arizona I need to pass emissions and thus the need to correct something with the carburetor or emissions and I am hoping you can help. I just bought this truck, I replaced the plugs, wires, rotor, cap, and made sure all hoses are connected. The carburetor is a Holley manufactured for Motorcraft LIST 50262-2 (E5HE-9510-MC). The idle was kind of high the first time I went in (~1500 rpm in park). The first emission test: HC (Hydrocarbons PPM) Loaded 185 (300 pass) Idle 275 (300 Pass) CO (Carbon Monoxide %) Loaded 2.53 (3.00 pass) Idle 5.2 (4.00 FAIL) I felt the idle was high and turned it down to ~900 rpm, replaced the PCV, Next test: HC Loaded --> 181 (OK) Idle 558 <--FAIL CO Loaded --> 2.08 (OK) Idle 8.37 <---FAIL BIG TIME! I have been looking all over the place to figure out how to set the idle mixture or where the screw is with no luck. Is that factory set? One last note. The previous owner put some type of hand valve between the PCV and the port on the carburetor. I did not find this until I was turning down the idle. It looked like it was perpendicular to the line (off) during the first test thus I opened it for the second test. I am unsure the reason behind putting a hand valve there? What do you think? Idle mixture adjustment? Timing? Any help would be great. Thanks again for your helpful site.