Save gas $ with Stage 1????

[svx_commuter]

Hi
I am trying to figure out if the ECUtune stage 1 will save me money on gas. I have an intake manifold so I can save $100 off the price. So the stage 1 will cost me $120. Premium is running about $.15 more than regular.
So if I run the chip in the regular gas mode and still get about 25 mpg then I have to drive how many miles to get back the $120?
$120*25 miles/gal / $.15 /gal =20,000 miles
Well that is less than a year for me.

Do you think my SVX will still get 25 with the chip and regular gas? From what I read the chip will result in richer burning fuel mixture and that means it will use more gas? Right?