chevy S 10 pickup v6 2.8l with emissions problem
 

I have a chevy s 10 pickup v6 2.8l that i have been having problems
with. the truck wont pass smog was way off charts so gave it a new oil
change and spark plugs. also adjusted the carburator. it now passes on
everything but Co2 at hi speed 2800 rpm. 2.69% 1.2% is what is needed
to pass. can anyone help me with this problem. just cant seem to get it
down another 1.4% :( thanks in advance