The wideband was calibrated when it was installed - thinking that was around 4 months ago. It's due for it's initial 3 month re-calibration, though it hasn't seen much actual use in the time it's been installed. It's on my todo list. The only other thing that could be causing it to read less accurately is it's location in my x-pipe. The recommendations are to avoid places where the exhaust system pressure might change. Unfortunately that's the only point in the exhaust where both sides converge.

I suppose the same phenomenon (pressure change) could be affecting the binaries which are located in the header collectors.

However, in general I would agree and go on to state I don't think I've ever seen a binary O2 sensor actually fail. Speaking in the context of tuning there are a lot of other factors that can cause them to appear to be causing a problem. Poor individual cylinder trims, poor closed loop settings to accommodate for header and / or cam, being relocated from factory placement, etc. All these are possibilities here. But I'm probably going to replace them simply because when I installed new ones back in 2017 I saved myself $20 by getting the Bosch units instead of the AC Delco 75s.

Before I pulled the engine apart looking for a mechanical problem I swapped back to my stock injectors. I should have reverted back to the factory tune at that point just to be sure, but for whatever reason just copied the injector and startup tables. I may repeat that test but revert back to the factory tune this time to eliminate my modded mystery injectors. I don't think they're leaking but I could have completely wrong offsets for them.

When I had the heads off I leak tested all the valve seats and found nothing wrong other than goopy fouling on the piston tops and in the chambers. This could have been from oil getting sucked into the intake ports from the rocker stud holes. I used better sealant on these bolts when it was re-assembled. The plugs didn't show signs of fouling and in fact looked relatively good - a light tan color on the porcelains.

Assuming it's not running miraculously better when I get back to it, and the injector swap proves fruitless I'm thinking I better start looking at the ignition system.

I'm traveling this week so will likely have no progress to report other than the acquisition of some ethanol free fuel.