code p1151

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having trouble , cleared code p0174 found vacuum leak , changed all 4 o2 sensors, cleaned MAF sensor and now getting code p1151. I checked all o2 sensor plugs , found 1 problem,1 plug was not tight, I corrected, but I'm still getting the code. the Truck runs better then new but won't pass smog test.i read somewhere about possible plugged injectors and or broken wires.