Nothing is more frustrating than getting answers from three different places -- that do not have commonalities!
Without testing the car myself, I could not really tell you what the answer is. My GUT tells me although the tune up, plug wires and injector cleaning are probably great services to perform for your Tucson that will improve performance, they probably do not specifically relate to your problem. I'm not sure why the fuel rails need replaced specifically, but it could be a cause of your issue.
Do you have any notes of what codes were in the processor? They should be able and willing to tell you this.