Trying to figure out where to look next. 2000 f150 4.6 4x4 auto. I am getting codes p1131 p0156 p0136 p1151. I have done the following trying to solve this and I dont know where to look next. I have changed the TPS, DPFE, both upstream 02s, gutted cats, cleaned the MAF, recharged K&N air filter, changed fuel filter, cleaned throttle body. Any ideas of what to look at next would be appreciated.

 

Look for vacuum leaks - especially the PCV elbow behing the intake manifold.