I have an 01 a4 quattro 1.8t with 60,000 miles... I have done some basic modifications: APR stage 1 tune, CAI, forge DV, Borla cat back exhaust, and a cat delete test pipe...All of the mods were done in that order. It ran well and pulled pretty hard for about a week...then the power started to become inconsistent, sometimes the turbo spool and DV were loud and very responsive and sometimes not at all...CEL came on showing a 0701 bank one lean and a secondary 02 sensor...I searched for vacuum leaks and found and fixed 2 of them...the car ran well again for 2 days and now I am experiencing the same problem and the same codes...if anyone has experienced something similar please HELP!

 

Did you gap the plugs down to .028"?

 

Yes I changed the gap. Every time I turn off my CEL the car pulls strong, sounds good and seems to run perfectly. As soon as I drive it for a day or so it looses power completely. At this point I am just trying to figure out what my next step would be...please help!