it's most likely your fuel fliter, if it hasn't been replaced from the stock filter than its probably clogged up. that why whenevr you use the fuel injection cleaner from costco it kinda helps push through, but you probably get clogged back up again after a couple of days huh. I would recomend the fuel filter be replaced and then do a fuel system cleaning,( you can buy these aat your local wal mart) and then change your spark plugs. then you should be running good again.