trouble with 02 sensors

[Mech13]

hello members I have a problem I need some help with.I recently finished a 5.3/4L60E transplant into my 69' El Camino with a wiring harness purchased from S&P.The problem is that my check engine light keeps coming on with codes p0134 and p0154 which translates to left bank / right bank up stream 02 sensors insufficient activity.Has anybody ran into something similar,I know it can't be the 02 sensors cause i have purchased and installed two new sets with no change to the problem.Thanks in advance for the help

[0rion]

are you running headers on that set up? Those codes are fairly common on even the LS1's after putting longtubes on. When those sensors get moved downstream they run cooler and you'll see the insufficient activity, switching, and heater codes from time to time. Some have had luck (myself included) by switching to bosch 13111 sensors which are vette rear sensors. *supposedly* they have better heaters in them.