Air filter change!

[Austin789]

Hi all, Yeserday I took my stock air filter out of the black box and pulled the cotton cover off and put it all back together... just to see if it would make a noise difference. As soon as I started my car I got a DPF warning coming up on the dash, why is this? I then put the cotton cover back on the filter and tried again and it doesn’t come up? Any advice? Does this mean I have to run the stock filter constaly as I’m planning on removing the box next week and replacing it with a Honda S2000 air filter and new air flow tube? 

(https://www.audisport.net/xf/threads/benjamins-s2000-air-filter-mod.118673/ )

  

 Thanks in advance, Reece