Originally Posted by Nixlimited

I'm not so sure it would. I suspect the majority of your driving is in closed loop cruise fueling mode where you are targeting stoich (14.7:1). You are only going to be getting that rich when under high boost. And if you are under high boost, then there is no point in thinking about fuel mileage.

Now, I have read about people lean tuning for closed loop mode (e.g. 15+:1). That's an interesting idea. It actually works OK from a power output standpoint, but I think the potential issue is the heat. Inevitably, some fuel is not burned, even when targeting stoich, and that fuel is being vaporized and absorbing heat. Take it away and that's more heat the block has to deal with. Not good on a VQ.