So I just purchased a 2006 Tacoma 4x4 with the 4.0L. The truck was too quiet for me so we added a Flowmaster 40 series in place of the factory muffler. Still too quiet - so we removed the second cat or premuffler (not sure which it was) on both sides that were located after the last o2 sensors. Now a couple weeks later I am getting a check engine light with the P0420 code. The only thing I can't understand is that although we removed the second cat/premufflers they were located after the o2 sensors so how could the computer now be throwing a code? Any help would be great I hate having the CEL light on the dash.