The HC and CO numbers are quite far from the limits. This indicates that you have good combustion of the fuel. The NOx emissions (after the cat) go up drastically any time the engine is running lean. An air leak is still a good suspicion. Engine timing can also play into this. If too far advanced, the combustion temperature is hotter and NOx production goes up. There is a control for the air/fuel mixture on the air mass meter which could be set a little lean.

A tune up is not out of the question, as they should check and adjust the igntion timing as well as adjust the mixture control. Still first I would look for air leaks in the air intake system.

Good luck,

Dan