Hey guys my name is brandon and i have a 2007 audi a4 b7, today my check engine light suddenly went on when i was driving on the freeway. 2 days ago i changed the stock air filter to a k&n air filter i think thats the cause of it and at the time i changed the filter there was a weird sound coming from the engine like it has a blow off valve sound when you take your foot of the throttle i was wondering if anybody had the same problem and what can i do to fix it. Any replies or suggestions is and will be appreciated thankyou soo much.

 

Double check all of your hoses, you probably pulled something off..