After thinking about it more... I'd only go after the upstream O2's after doing the basic maint/repair stuff, like plugs/air filter/fuel filter/check injector voltage and pressure leakdown/etc.

 

Also, check the fuel filter!!

 

fuel filter can cause that. If you have 50k on it I'd change it. hell change it anyway. I used electric motor parts cleaner from the parts store and just sprayed down the maf real good.

 

i just broke warrenty i have 36100 on it today. It has been out of warranty for about a week now. but anyway the plugs and wires should be good still you would think. I am going to change them just didnt want to do it right now, i was going to wait till this summer.

 

driving seems the same also. It still moves just like it did befre the milage change.

 

I would first check the MAF. You should still have a lot of miles left in the stock plugs and wires IMO. Check for exhaust restriction. Make sure to check the intake tube connection around the throttle body if you removed it.

 

so if the filter is dirty than the performance would go down along with the mpg right? cause i'm in the same boat and i've got good power just crap mpg. thanks

 

Same here. I recently changed my plugs and wires and it seemed my mileage went down. I know part of it has to do w/ the tall tires, but my performance is still real good. The only thing else I've done lately was put an Aerochamber on. I was thinking my O2s might be getting lazy, 136k miles.

 

Winter gas really sucks too. Could just be that?

 

I have a thought??? KEEP YOUR FOOT OUT OF IT!!!!!!!!!!!!!!!!!!!!

Jim