i have had this problem since i bought my truck about a year ago and i cant figure it out. if i drive a constant speed of 55 or faster for very long the check engine light flashes a code and it is the O2 sensor. all i have to do is let off the gas pedal and step back on the gas again and it goes out. a few minutes later it is on again and so on and so on and so on. i pulled out the old O2 sensor last winter and the thing was pretty distorted and twisted, (i never seen anything like this before). i replaced it with a brand new one for my truck. and it has not helped at all. same problem nothing changed. im only getting 14-15 miles per gallon. truck runs smooth, very dependable. plugs look good and has a recent tune up. im trying to figure out the O2 sensor hoping this is my problem with the gas mileage. my truck is a 86 rte 4wd with automatic. i realize i am only suppose to get 20 mpg with this setup but as i said im only getting 14-15 and that is all interstate driving and driving 65-70 mph and not romping on the gas at all. any suggestions.

im at the point now that i would be willing to trade for a 4wd toyota without the turbo just to get some gas mileage, because im driving about 350 miles a week, and with the price of gas it it killing me