Hi Zeracer,

The fuel tank was half full of unknown age fuel. I stopped at a gas station that is usually busy (should be reasonably fresh fuel) and filled full of premium.

I've been thinking on this, is it possible that since I had car trucked here to Colorado from Delaware and I had driven very little (maybe 10 miles total since it arrived) that the engine control unit just hasn't reset for the higher altitude? I'm wondering if it takes some time for the ECU to realize conditions have changed. I haven't been able to drive due to no license plates - have to have emissions certificate in hand before plates are issued.

There was a long line at the emissions test center, so car was idling for an hour or so prior to being tested. Colorado does a dynomometer test, varying speeds and loads while exhaust is being sampled/tested.