I have an 85 B2000, fresh tune-up, new O2 sensor, new catalytic converter but it's won't pass California smog check. CO at idle is 1% fine passes smog but at 2500 RPM CO is 6-7%. So whatever is in the carb to lean it out at higher RPMs isn't working. Anybody have and ideas or experience with this type of problem? Thanks for your help!!

 

my advice is to get a bottle of chemtool b12 (for the gas tank) and tune the carb a tad on the lean side for the test. go on a hot engine and a low fuel tank. if i have california numbers right, you aren't too far off from good numbers and this will bring you down into nominal.

 

I did all of that before I went in for the smog check. The only adjustment to lean out the carb is at idle which is not the problem. The problem is at 2500 RPM where the CO reading is 6-7 % and it needs to be 1% to pass.

 

CO is Carbon Monoxide...
Your catalytic converter turns it to CO2(Carbon Dioxide), but it seems that's not happening at the high end.
It looks like you aren't getting enough air into the exhaust to aid the conversion.