Possibley alternator?

[Cbballplaya]

I have a 1989 camaro RS that i bought last summer. The car was stored for a couple years and has never seen winter. Last fall and still this spring the service engine soon light starts flashing occasionally. I ran the car for codes 3 different times with a diognostics machine but nothing ever came up. I replaced plugs, wires, cap and rotor, and the fuel filter. I actually changed the fuel filter 2 or 3 times, after everytime i did it the car was fine for awhile. I don't know if it was a coincidence or if i just have a bunch of crap in my gas tank that is plugging my injectors. I was just wondering if any of you guys out there have had any similar problems and if so, if it could be the alternator.
Thanks alot,
Chris

[jackmalone2001]

check your oxygen sensors

[miecow]

read the codes when the check engine light is on

[Cbballplaya]

already replaced the O2 sensor and no codes come up