I am new to the forum but have heard really good things...To sum up my issue. I bought my second taco from a guy a few weeks ago and the check engine light was on...he told me it was the downstream 02 sensor which I bought for 100 bucks and replaced thinking this would solve my problem. I them went to advance to have the code turned off and it showed P0440 and a few others I cant remeber. The truck runs really good and seems to get good mileage- no sputters or lags...just wondering what to do next?? I am praying to god it is not the cat. I have a 30 day tag and will be registering the vehicle in TN where I do have to pass emissions. Any Ideas??