2002 Ford Taurus Emissions Instrument Light

Few weeks ago I had my emissions light come on following rough idle when I came to a stop. I took it to a friend that cleared the code and had me put some gas cleaner in it. I did so then filled up with E85 fuel. Problem seemed to vanish. However, a week or so later it started to idle rough again and my light returned. The mechanic then took it in and cleaned the fuel jets and cleared the code again. It came on again today, following a sudden rough idle. I have not had a tune up for about a year and he's thinking to try that this time. I have also read that it may be the vacuum lines coming from/to the manifold. Is it ok to drive in the mean time and what do you suggest I try next? Thanks!