hey all. my first post. just wanted to let everyone know who may be interested in a DP fix for n55 motors. I believe no one has made a o2 sim for downpipes. I have a 2011 335i with n55 and I'm running a VRSF downpipe and no other mods beside CDV.
I have found this to work on my car with no check engine light for 80+ miles
http://www.amazon.com/Minicat-Sensor.../dp/B008UF1T2A
hope everyone finds this as useful as I did!