I think Corey's 98 has a lot more miles on it than yours does, and his bottom end is still original, you might want to try some engine additives, but still, first thing you need to do is to get that engine running correctly, you aren't running lean, from the description you gave me you are definitely running rich on that bank, that bad O2 sensor is telling the computer its lean, so the computer is trying to enrich the mixture, that is why its running rich, too rich a mixture can even cause stuff like valvetrain damage, I thought you were going to take care of this a while ago?? Here is a test for a VERY rich mixture: Pull your dipstick, smell your oil, does it smell like gasoline? If it does your mix is so rich that raw gas is seeping past the piston rings and going into the engine oil pan, this can cause all sorts of problems by thining out your engine oil, also as soon as the problem is corrected, do an oil and filter change if this is the case, get that oil out of there!