Ok i think i got this millage problem figured out, well maybe? I knew i had a leak somewhere but now i know for shure. i was sea foaming my intake today and found that my exhaust dough nut was leaking bad! bad enough for smoke and sea foam to come out at a good rate. my o2 sensor is about 1' and 1/2" behind the flange, could this leak give my sensor a false lean reading? anyone else ever had this prob? Thanks again for everyones input!

 

Hopefully it is.