NorCalAnthony

Hey guys, I'm going to be using a set of C6 LS3 exhaust manifolds for swapping a 5.3/4l80e in to my '89 K5 and had a couple of questions about the O2 sensor locations. The C6 manifolds have the O2 bungs built in above the outlet flange instead of being in the exhaust piping 6-8" down stream of the outlet like on the donor truck. Will them being that much closer to the engine affect anything (like tripping the CEL) or require any additional tuning for them to read correctly since I'm using the 0411 PCM from an '02 Silverado? I've been searching around on here but everything I'm seeing is for people moving them further downstream or installing wide band O2's... Here's what the C6 manifolds looks like for reference:




For the rear O2, is there a set distance it needs to be from the engine or cats or do you have some wiggle room? I've heard they can be pretty finicky and trip CEL's if they're too far away but haven't been able to find out if there's a sweet spot that it needs to be in yet... On my donor, it's on the DS exhaust tube right before they merge at the Y so I'm hoping to keep it pretty close to that when we run the new exhaust in the K5 but I'm not sure how that'll work out looking at how ugly the current exhaust is ran to fit around all of the 4wd stuff...