I have an AC question for a '99 A4 Avant... I removed the stock airbox and replaced with an aluminum intake and a K&N on the end. I noticed when the AC is in recircuation mode, the tube that was connected to the side of the stock airbox is sucking in air. I thought with recirc. on, it wouldn't take in fresh air, but that's what it seems to be doing. For those that have removed the stock airbox, what did you do with the AC tube?

 

im not sure if were talking about the same thing here but i know on mine with the EVO intake they supply a mini filter which goes onto a breather hose... im assuming thats what your talking about... il see if i can find a picture

 

It's not for the AC. It goes to the secondary air injection pump. The pump supplies air to the cylinder head and reduces your emissions. All you need is a breather pilter that will fit in the hose. Do not run your car without the filter.

 

What size breather fits on it?

 

I just ordered a stock air box to replace my hacked one and its off of a 99 that doesnt have the port for the 2ndary air pump hose, i would like to know exactly what breather filter will work too.
So... Wait... I thought 99's didnt have the 2ndary air inj pump??? Did some have it and some not???