1999 Saturn SC1

Hi! I own a 99 Saturn SC-1 from last 2.5 years. I got my spark plugs and wired change 1.5 year back. Fortunately I had no other problem til now. I have done all my oil changes regularly. But now I have some Problems and some Questions.
1) During last week my car would not start for an hour after driving for 10 min and then shutting down the engine. I got it checked by a mechanic who said my starter has gone bad. I went to Autozone to get my electrical system checked where they some how sold me a fuel system cleaner. Since I waited in the store for one hour I bought it and put that Lucas fuel system cleaner in my gas tank and co-incidently from that day my car is working. Even my mechanic was surprised.
BUt NOW I FEEL AS IF MY ENGINE IS rough WHEN I USE IT AFTER A GAP OF AROUND 6 HRS. IT HAS STARTED DEVELOPING EXTRA VIBRATION USUALLY IN PARKING. AFTER DRIVING FOR A WHILE IT GOES.
My mechanic suggested I need a Tune up. But I am just wondering that do we need a tune up in less then 1.5 yrs.
2) aLSO I WAS THINKING IF THIS NOT A CASE OF uncleaned FUEL system injectors.
I would really appreciate any help.