1990 Gutlass 3300

had a recent and sudden loss of power, the engine is running rich and missing baddly. the rear bank of plugs where wet when i checked them. recent tune up/ fuel filter change ran fine for a few months. changed O2 sensor no improvement. early on i could manually shift to cause higher rpm and the missing cylynders would kick in like a turbo. now nothing. no trouble codes either . any ideas?

I will be checking the coils tommorrow..