GAV Question

[Kurt in NJ]

I did testing on emission machine under load , on 'regular" gas I got 3-4% CO with GAV closed, ran fine, gas mileage over 20mpg
Then NJ got 10% ethonal, this made the car too lean with the GAV closed, 0,5% CO (car would pass emissions as a 90s car), good running took 1/4 open up to 60, 1/2 above 60.
I found that 3-4 % the plugs would burn light tan, at 0,5%-2.0% they burn pure white
When I used gasoline with over 25% diesel it would take 1-2 turns to even run