I have to disagree , I have tuned 5 or 6 TC engines , and have aleaviated this so called normal problem , I achieve this by doing a 13.1 a/f and advance the timing 2 deg in the 900-1250 rpm range , this also make for a easy cold start. , Again the reason why the 2010 models changed the location of the 02 sensor is because the heat realted issues of burrning up 02 sensors ,moving the 02 sensor down stream is really not the most ideal location for a 02 sensor to sense the true amount of oxygen in the exhaust,but then again we are dealing with a semi closed loop system .But this is only my opinion and personal results .