Multiple problems w misfires // system too rich - now strong gas smell and consistant 4, 5, 6 misfires

Have been having ongoing problems with drivetrain, first I started having error codes which indicated random misfires and drivetrain too rich. Following the advice of the information I collected on forum sites, I Have since replace the EGR, the EGR pressure sensor, the PCV, cleaned the MAF sensor, replaced the spark plugs (went from autolite to motorcraft platinum), checked for any intake hose breakage and/or leaks. Now, I am getting a consistent error misfire detected on 4, 5, and 6 cylinders. This error does not appear to occur while the vehicle is in motion but rather when it is idling or stopped at a light. The engine starts to feel like it's going to stall at times but more on idle than any other. The other thing that I noticed is there is a strong gas odor in the engine and cabin. Upon looking for the cause I found that there was gas runoff coming into the PCV area. I am getting extremely frusterated because although all of these issues may be stemming from the same problem - I cannot figure out what is going on. Any suggestions would be appreciated.