1999 Pontiac Grand Am Engine Misfiring

About a two months ago, the motor was running very rough and engline light came on. I took it into the shop and they determined that the #1 Cylinder was misfiring. The said that there was oil in that cylinder and that I would need to change the engine because the seals were bad. Instead, we replaced all 4 spark plugs and cleaned out all the cylinders. That seemed to fix the issue at that time. It started to show small signs of a misfire for about a week now but no lights came on. Today, it had alot of hesitation on acceleration and by the time I got to the residence, it sounded like more than 1 cylinder was misfiring. It actually won't start unless I hold gas peddle to the floor, but then idles real rough and stalls. Any thoughts? I was also running fuel injector cleaner through it, and that seemed to help at the time.