I bought a 2004 Chevy 2500HD 4x4 with a 6.0L and 4L80E combo.

It has some light mods done to the powertrain.

-Full Bassani exhaust from the headers back.
-K&N cold air kit
-Small 210/218 .551/.551 on a 116*
-And a stall of unknow origins. Somewhere around 2800-3000 I would guess.

My Parents drove the truck back from FL a couple weeks ago with out any problems. I have been driving it every since. I got caught is a huge down pour of a rain storm and splashed aot of water up inot the engine bay of the truck. Every sice the rain strom my truck has had a low rpm low load miss. It just happens upon take off and when the truck kicks down into OD cruising. I have changed the plugs and wires, and it did not help.

EFI/LIVE scan shows I have DTC's:
P0135 "02S Heater Performance Bank 1 Sensor 1"

EFI/LIVE systems test reluts show I have one 1 sensor heater bad.

I put in a new OE replacment O2 sensor. Bank 1 is reading lean. I checked the system test and all is showing good.

DTC:
P0171 "Fuel Trim System Lean Bank 1"

For the sake of argument I swapped the driver front O2 with the passenger front O2 and it is still the same thing. Bank 1 is Lean. I dont understand how Bank 1 is super lean and Bank 2 is only slightly lean. I mean it idles at 21% on Bank 1 and 2.3% on Bank 2.

Something has to give.avent set up my PID tables yet or doen any real tunning on the truck. I just found it odd to be off by so much from the driverside bank or the passenger side bank. I have checked for leaks and everything. I am at a loss.