I have run my truck with an actual air fuel meter in the exhaust. It's a very accurate tuning tool. Using dual W-1 Carters, its easy to adjust for rich or lean by raising or lowering the metering rods. It only take .020" to see a difference. I tuned for highway speeds in which I drive the most. I then set the idle mixture screws. With two of them, and a very accurate gauge, I can get them dead on even. Just the slightest twist will change the fuel ratio more then you think it does.
Joe
