Hey guys im having a bit of a struggle trying to get my truck running. I had my tuner come out twice now and hes getting absolutely no reading on my upstream 02 sensors (and yes theyre plugged into the correct locations) as well as cylinders 5,6, and 7 were stone cold dead after getting it running for a few moments. We CANNOT get it to run correctly since he has no info to go off of with the dead 02 sensors. it had previously working 02s in that I replaced with brand new 02s and still its flat lined at 460-500 mv.

some background on the truck: its a 2004 gmc sierra 1500 that i swapped a mildly built lq4 6.0 in. it has longtube headers and straight pipe dual exhaust with full bolt ons, cam kit and a bunch of other goodies. it did have a 4.8 that was also mildly built and ran great last summer and since ive thrown in this 6.0 and built trans we haven't gotten it to run correctly yet.

due to the dead 02 readings it is just dumping fuel in and eventually with some wire wiggling we got cylinders 6 and 7 to fire but 5 is still dead. We're only having missfire issues on bank 2 (passanger side) and i have no idea what to look for. my only next step is to rip off my intake manifold and make sure i have good grounds and clean the mating surfaces but other than that im at a loss. all 02 fuses are good so i have no idea whats going on here.

Anyone encounter this kind of problem before or have an idea what i should look for? im trying to find all of the ground locations and make sure they ALL go back to stock locations incase some got mixed around but i just cant explain how both 02s are completely dead.

Thank you in advanced guys I need my baby running again!