Gas Mileage Improvement after New Cat, O2 Sensors & V4 Chips

[gsodonis]

Two weeks ago, I replaced my stock main cat with a Magnaflow dual inlet single outlet cat. The stock exhaust (pre-cat pipes) had a bunch of cracks at the brackets that bolt to the tranny that I welded up while everything was apart. That same day, I replaced my original O2 sensors with new Walker ones and installed my ECUtune Stage 1 V4 chips.

From the first tank after doing all three things, my gas mileage has improved a consistant 12%. My average mileage before the mods was a solid 22MPG (+/- .5 MPG). Since the install, my last four tankfulls netted 25 MPG (+/- .5 MPG). My commute is 80% highway (cruise set at 80MPH), 20% city (leadfooting it to hear the Stebro).

I'm not sure to which mod I should attribute the gains. More than likely, it was a combination of all three. Has anyone else seen improvement s in mileage from doing any one (or combination) of these mods/repairs? The V4 chip benefitting mileage is suspect as it actually makes you want to bury your foot in it more, not less.

I average 30,000 miles a year. At $2.00 a gallon of 93 octane premium, my increased gas mileage will save me $327 a year. The cost breakdown:
Magnaflow Cat: $64.00 delivered
V.4 Chip Upgrade: $59.00 delivered
New Walker O2 sensors: $128 delivered
Total parts cost me $251.

It's not to often a mod/repair pays for itself.