I put in my new k&n filter today which was a success and the car is running great but I noticed a small half black half white valve on the top of the airbox that has a pretty good size hole in it and is cracked. Does anyone know what this valve is ?? Is it a must fix immidiatly?? BTW my car is a 2003 A4 1.8t if that helps I think it may be just a check valve but I wanna make sure.

 

Your description sounds like a check valve, but it'd be easier to be sure of what you're talking about if you could provide a picture of the area in question. Presuming it is a check valve, they're pretty inexpensive to replace, and should be replaced as soon as you reasonably can. It's not like the engine is going to explode with it being broken, but it could be the source of a vac leak and/or other problems, so you don't want to just leave it that way, either.

 

http://i301.photobucket.com/albums/nn42/PineGroveDave/IMAG0894.jpg

This is the picture of the valve its the one with the Orange silicone on it hope that helps thanks

 

Yup, that's a check valve. This thread has all the info you could possibly need on it, including where to buy replacement check valves and vac lines inexpensively:

Engine Strengthening by a4darkness

 

Thank you for the reply I really appreciate the help