2.5 2006 volkswagon jetta stalls and has a rough idle?

So I've been trying to figure out what's going on with my girlfriends car. When it starts itll idle horribly and eventually stall. When I unplug the maf sensor it idles almost perfectly in limp mode, but it still has a loss of power. I did some research and found out a lot of people have an issue with their PCV valve. So I installed a new valve cover and when I started it up it still ran the exact same. So I tried replacing the maf sensor but that didnt help. I forgot to clean the spark plugs and coil packs. Do you think that would make a big difference? Plus I forgot to check inside the throttle body for oil.. has anyone had this problem before or can point me in the right direction? I dont want to take it to a shop until I've tried everything.. btw I dont remember the codes exactly but I do know it threw codes for all 4 cylinders misfiring and intake airflow leak.. oh and what's a good way to check for vacuum leaks?