I've just brought a new O2 sensor and will change it soon, will let you guys know if it has helped my wallet. Mods that I have are a 3" exhaust from turbo back, FMIC, pod filter (with CAI set up), runs at 10 psi. I've also changed my fuel filter recently and my plugs as well, and am using an injector cleaner regularly (Redline). I also have an Emanage but it isn't tuned yet (this factor won't be helping me any either).