Hey guys, im looking for some advice to help me get some better gas mileage out of my 5.2. I was getting only 9 or 10 mpg, then i cut my muffler out and patched in pipe, its a full tailpipe, cat and o2 sensors are still there, now im getting 12mpg. Maybe once a month my check engine light comes on, i had it scanned and it said an o2 sensor was bad, im kinda thrown off by it only coming on once a month, but i guess i should replace it anyways. I have a vaccum leak, i dont know if that would cause it too or not. Any advice as far as a cold air intake or anything that would help? thanks guys!