89 Honda Accord failed for emission test for CO, in both 25/25 and 50/15
catogery. I replaced the air filter and used car guarantee pass and drove
300 miles. When I took my car back for emission test it passed in 50/15,
but failed in 25/25, here are results

Test 1 --> 2.66 -- (1.16 allowed) FAILED--> 2.83 – (1.05 allowed)
FAILED
Test 2 --> 1.91 – (1.16 allowed) FAILED --> 0.12 - (1.05 allowed) PASS

Can anybody suggest me what are the things I can fix and test for
emissions again? Since it passed the 50/15 test I was hoping this is a
minor problem.
I am planning to change spark plugs and PCV valve.

Thanks