If you want some improvement, use ECO map if you have it in your custom map...
I have 3 slots in my custom map, 0 is ECO (ca 7 psi), 1 is stock boost 11psi and 2 is 14 psi map...
I drive it on ECO map sometimes while in the city, car is lazy like a cow (throttle response slow, boost max to 7 psi), but it improves fuel consumption cause you cannot burn the fuel actually...
But when I drive it on high boost map, I want to use power even more than before so fuel consumption gets worse...
Theoretically, consumption would be better if you would not exceed stock boost cause of leaner mixture in tuned map...but I think it's just theory...