[nUcLeArEnVoY]

Running lean is often blamed for running hot, when in reality it doesn't make much noticeable difference. Usually something far simpler is going on.

The biggest tuning-related issue when it comes to engine temp is ignition timing moreso than fuel delivery. Retarded timing tends to cause engines to run hot since it doesn't allow full evacuation of exhaust gases due to the delayed spark during the compression stroke. I've seen videos of headers glowing orange at idle speed because of retarded tuning.

Slow temperature rise at highway speeds can be normal for some cars simply due to higher RPM = more work and heat generated, but eventually it will level out and stop rising that far past the thermostat temp. But if your engine temp rises out of control at speed and doesn't stop, then it could be a radiator issue, blockage somewhere, restricted airflow, simple case of air in the system, a lower hose collapsing, thermostat not opening, or bad water pump - Pontiacs are special with water pumps in that they need proper clearance between the impeller and divider plate to ensure adequate flow.

Check all the above basics first. In the case of restricted airflow, make sure to see if your car came from the factory with a front air dam. If so, make sure you have it installed. On some cars, it is essential to redirect ram air to the radiator at speed.