P0136 again

I would like your suggestions please. Just purchased this truck and I have to say I really like it! The freakin CEL is killing me though, its a 3.4 2003 with 195K. The first code was P0031 so I replaced the O2 sensor in front of the Cat. Shortly there after the CEL came back and now P0136 appears. So I replaced the rear O2 sensor. Both have been Denso sensors. Yesterday I unhooked the battery to try to clear the ECM. That cleared the light and the very first start up the truck seemed to idle a bit lower than normal. I shut it off and closed the hood and the truck had no power to anything. So I pulled the battery cable again and reattached it. Truck started and seems to run nice and smooth. But the CEL is back on, and the code its showing is P0136.

I'm not sure if the exhaust system thats on it is stock as the muffler is about 2 feet down from the last cat and the exhaust lets out under the bed. It also has someone's Cold Air intake on it. So I have read that the higher flows (possibly) could be causing the 02's throwing a code.

What should be done next? The truck seems to run great otherwise, its the *&%$#* light that is making me nuts.

 

I believe I have resolved my issues. Reinstalled the o2 sensor after filing down the flange on the exhaust pipe, tightened the sensor with a new gasket and now after 100 miles no issues. Must have been leaking!

Good to go now