emissions too high

my bronco, 1985- 351 4-B carb., did not pass emssions last week. a year ago it would have passed for a car's standards. this year it was two times the max on CO- carbon monoxide. i have not done anything to the bronco, and i've only put about 1000 miles on it. i do not detect any loss of horsepower.
your thoughts please...
thanks.

When I was a state inspector years ago, we would tell customers who failed there inspection to drive it very hard "obey the law":evillol: :evillol: :evillol: on there way to inspection station. With such low miles it probley needs to be driven "hard" for a few miles, check the air filter, PVC, plugs. These are the easiest and cheapest to do.