2001 bmw 325ci engine problems

[michaelbmw325ci]

i have recently purchased a 2001 bmw 325ci. 171k miles and a 2.5l straight 6 cylinder. i had it tested for emissions and it failed. the check engine light is on and the codes coming up for it are for the coils, spark plugs, pvc valve, o2 sensor, and mass air flow sensor. ill be driving down the road just fine and all of a sudden it starts surging and sputtering. at this time it has no power and wont go faster then 35-45 even with my foot to the floor. its a 5 speed and seems when the lower gears are used, its a lot worse but as i get to higher gears, it steadily gains speed. ive changed the spark plugs and wires and no change. when i went to take the spark plug 6 out, there was water in the port and after clearing the water and removing the plug, it had rust on it. heres where it gets weird. itll be idling at 6-700 rpm and sounds like its misfiring. the emissions test said cylinder 4-5-6 were misfiring so that would explain that but i tried unplugging coil number 6 and the car then ran smoothly and the rpm came up with no sputtering. anyone have any ideas?