Engine sputters, engine light flashes and seems rich under wot

[031500HD]

2003 Chevy 1500HD 4x4 CC 6.0 LQ4/4L80e K&N CAI, efans, 1 5/8 LT headers, 3" true dual full exhaust w/ X-pipe and flow through mufflers. Truck runs much better than it did stock with the listed mods and the base tune I have on it. Things were good until I installed the headers and exhaust (was stock maniflods and exhaust). Now the truck seems to run rich at idle for no apparent reason at random times (.68 Lambda) and has obvious misfires. Then after getting the rpms up a little while driving, it goes back to 0.97 - 1.03 Lambda and clears up. Did a wot run today and in 3rd gear the wideband read .79 which is quite a bit richer than the previous .83 - .85 I was seeing before the exhaust. The check engine light also flashed at the same time and the truck felt down on power. Oddly enough the Injector duty cycle was way up over what I was seeing previously (truck has stock injectors). My understanding tells me if anything the engine would likely be more lean, not more rich, after freeing up the exhaust. Looking for any help and any insight as to what might be the root of the problem.

[5FDP]

Double check for leaks on the drivers side. The fuel trims are far more active on that bank, a few times maxing out at +25%.

Stock injectors are almost at their limits with headers/exhaust work on 6.0's, so seeing 90% duty cycle seems about right. The 100%+ is kinda funky though. The possible issue on that side also makes your bank 1 injector pulse with avg almost 2.0ms higher on that side sometimes which cause the duty cycle to jump higher.

Past that have you been tuning the MAF/VE with your wideband to square the rest of the fueling away??

Also, if the rear o2 sensor where removed completely you may want to install them and just hang them out of the way. HP Tuners can't shut off a cat test that happens with the circuits are left open. Had this issue on a 2006 truck I owned along with helping a few others. Hooking the sensors back up stopped the cat test that would randomly cause the AFR to go lean/rich.

[031500HD]

After checking, I think I may have an exhaust leak on the driver's side. I did a lot to the MAF using the wideband before the exhaust and headers but have been fighting the rich condition so have not touched it since. No tuning to the VE table yet. Rear o2 sensors are hooked up and tie strapped out of the way. Seems like the majority of my issues may be related to an exhaust leak?

[jaysonnewellolson]

you might need new spark plug wires mine did the same thing with the dynateck header untile i installed msd wires the spark was arcing to the header tube. it can put you into a limp home mode too.