227K miles, failed for high HC and CO (Colorado GPM):

• HC was 2.25, limit is 1.20
• CO was 76.4, limit is 15.0
• NOx was 0.86, limit is 2.00

Replaced O2 sensor, cleaned throttle body/IACV/FITV, retarded timing 2º, adjusted valves. All valves were tight except for two intakes; several exhaust valves were < 0.006. Passed retest this morning:

• HC is 0.17
• CO is 2.19
• NOx is 0.66

Ran it at 80mph on the interstate for 20 minutes before the test, and kept the rev's above 3K rpm by shifting to D3 and 2 on surface streets. Waited 20 minutes in line but kept the rev's @ 3K rpm while waiting. The cat stayed REALLY hot...there were heat waves rolling out from under the car. I'm surprised the NOx dropped too.