Well I can talk from first hand experience.
With the B ama 87 perf tune I see between 1-2mpg more than the car was stock driving as close to possible the same roads, ie work and back, 60% highway 40% city.
With the B ama 93 Race to I get the same gas mileage as stock.
With the Bama 93 Torque tune I get a little less than stock. I think I can explain this one, because I think this tune opens the throttle early to give you a feel of more low end so coming off a stop you use more fuel than normal. Multiply that by how many time I have to stop and you get worse MPG.
As far as why the 87 tune is more I would say it is because of the revised fuel tables, leaning the mixture makes more power so thhe fuel tables are different and if takes less throttle to make the same power as before so therefore less rpm and less fuel. Biggest gain would be on the highway using this theory, which has played out for me.
In order to save more gas I would suggest a CAI, 87 octane tune, UDP, and aluminum driveshaft, BMR sway bar delete/rad support, and removal of the spare.
The CAI and tune are described above and everything else reduces parasitic loss and/or removes weight all of which will help MPG.
Or you could just shift sooner and accelerate slower and keep to the speed limit. Cheaper and works just as good.
But it is funner to Mod so to each his own.