Keeps setting check engine light; code P0300

Sets codes P0300, P0301, P0303, P0305. I have used stp injector cleaner in gas tank every few fill ups; for a while this fixed for a month or so but now only goes away for a couple of miles. I took to shop and had injectors cleaned only lasted one day. That day I drove the car about 40 miles mostly highway with no problem. The next morning I drove about 8 miles city streets when it set the same codes again. After warm up it has a rough idle, and when accelerating from a stop I have to push gas pedal more than normal as it is sluggish until the rpm get a little higher then it takes off. It always set the same codes.

Thanks for any input you can give me as I do not have the money for new injectors unless I am sure that they are the problem.