Spark Plug Problem 99.5 jetta 2.0

So my 99.5 jetta 2.0 was idling a little funny and i have not changed the spark plugs since i got the car in december so i figured it was long over due. I replaced the old spark plugs with bosh platinum 2 i believe and when i first started the car, it seemed perfect. then i shut it off. 5 minutes later i got to test drive it, and the idling has gotten worse and it sounds like it's running on three cylinders. i have no idea what has happened and have double checked everything. then my check engine light went on. i turned it on today for a few seconds, and there was like an air whistling sound coming from the engine too. if you know anything, please help me. thanks!

check for a vacuum hose off