I know this one's probably been done to death but please indulge me;My girlfriend has a '92 forerunner and the check engine light came on,it has the 6 cyl.engine and 146,000 miles on it,I 've noticed a decrease in the mileage and a strong fuel odor.I suspect an oxygen sensor,for the more educated in this group,is there anything else I should look into?if I'm correct and it is an oxygen sensor..any tips on how to replace it and it's location would be greatly appreciated,TIA