Can someone help me narrow down sputtering/stalling causes, I've checked a few

[Musclehead]

95 Altima with 55,000 miles- Eratic sputtering/loss of power sometimes stalling up to 4 times, always restarted. I've searched other posts and have done what I could. First off the ECU led light will not give me anything, it will clear the check engine lightly briefly but will not light up. The alternater was tested and is good. The fuel filter was replaced. I took off the distrib. cap and rotor and cover, it is very clean no sign of oil. Cleaned the MAF with MAF cleaner. I've found now that it sputters like crap at 2000-2500 RPM and if held there will occasionally cut out and die. I've run out of options to do on my own and have to take it in, we need the car and it's become too dangerous for my daughter. Earlier when they did have it, they were unble to duplicate the problem (it's become worse now) but they had said it's either the MAF, O2 sensor or anti-knock sensor, or fuel pump. What should I have them do or not do and in what order? I don't think it's a pump at 55,000 miles? Sounds like MAF problems are more related to issues from other defective sensors? From what I've read here it seems like this is an ongoing problem with Nissans, but it looks like I'm going to end up buying some pricey parts.