97 SES light (tried numerous things)

I have a 97 Conty that the SES light keeps coming on. I reset it, and 2 or 3 days later it comes on. I have had the code scanned, and it is the infamous 0174, bank 2 to lean. I have tried finding a leak in the hoses or t fitting for the PCV valve, changeing the PCV valve (although it is one of the universal types, where you plug the upper hole and use the bottom hole, but the plug goes in awful snug), I have had it to my local mechanic (who is very good), and he stated he found the O2 sensor to be OK, and he gave it a "smoke test" (any clue what that is?), and found that to be OK. So, what else should I look at? Is there a fuse that I can pull to turn off just the SES light? Any insights would be appreciated! (And I am now running premium gas, which I thought may be the problem when I was running regular, but it's all premium now, and it still comes on)

I have the same car and my SES comes on once in awhile too. Mines was o2 sensor bank 1. Goodness, ya think they put enough o2 sensors here? 4 of them! Mine came out to low voltage,etc,yadda yadda. My mechanic check it out for me,cleared the code and it came back on. He suggested that I use some fuel injector cleaner in addition to some dry gas. Strangely enough that did the trick. He asked where I got my gas from, it's always premium from Mobil. I guess the thing is, which Mobil. Hmmm...interesting to see how "pure" the gas is. It's aPITA and each time it comes in I do the same trick. It shouldn't be that way, but I think I narrowed it down to which stations give me the most SES light-ups. It might be a coincidence, but I hope someone else has a better answer! I don't feel like spending ~$80 bucks just for one o2 sensor that testets out good. I checked several lincoln sites + dealer mechanics(not sure if I can trust them) and they recommend to change the 02 sensors (that's 4of them!) at 75,000 miles! Shesh! Let me see 4x $80= $320! ( that's parts cost from an auto store) Shesh! Dealer mechanic claims that having new 02 sensors will offer me better gas milage. I've had bad o2 sensors go on me before, the car bucks, chugs,etc. Not sure about all these computer chiped cars now! Shesh! I feel your pain brother!