Pontiac Grand Am

Pontiac Grand AM 2000 89k miles 3.1v6

I recently had a tuneup that served as a tunedown: spark plugs + wires, fuel filter, pcv valve all replaced. It started running a little rough during breaking and idle. In addition, there was a faint fuel (oil?) Smell which entered through the passenger ventilation after idling for a while.

So I took it back. It had a code 301 - misfiring cylinder 1. The diagnostics reported an occasional (< 1%) misfire on some of the other cylinders, but there were no other codes. The repair shop replaced the plugs and wires. The faulty cylinder 1 seemed fixed but the rare misfires were still there.

But I have noticed that the fuel smell is still present. What is the most likely cause?
December 23, 2006.

Was the performance problem there prior to the tune up?

Why did you do a tune up?