The CAI should have lowered your mileage since it introduced more air into the system and the computer compensating by sending more fuel. However, your driving habits may have changed because of the more power. The tires and oil probably made a difference also. I caution against using the 0W30 for a few years as the "0" may be too slippery for the GP engine.

I have the thrasher CAI. Those do make a big difference and give it that Darth Vader sound.