So how much timing at cruise is too much? I've added about 10 deg to my cruise timing cells so it's now in the 35-38 deg range, and there was a negligible increase in the average MPG at cruise (64-66mph). I'm logging MPG with a calc pid. The increase was about 0.4 MPG which could be caused by other variables. I did however drive the same exact route at the same speed, roughly same outside temp, etc.

I made a map of MPG versus RPM and grams/cyl airflow (same as spark tables) and filtered out non-cruise data. Is there a better way to see the change in fuel consumption?