Join Date: Aug 2010
Location: Freakin' cornfields
iTrader: 1 reviews
Thinking out loud, and from what I had seen, is if the injector timing isn't dialed in perfectly it's going to want more fuel than it really needs, as some is going to go out the exhaust due to overlap. It might require a tweak in that direction, depending on what it's set at now. The variation bank to bank definitely indicates there's some difference there, though how I couldn't say. If the exhaust wasn't touched that might rule out sensors or exhaust leaks. It would point more toward something that would affect one bank but not the other, like an intake manifold gasket, or cam timing.
...but even then when my injector timing was way off I didn't pop any misfire codes. So while it may be something to address it may not be the root cause. Have you looked at/inspected your crank trigger wheel? The engine is going to base misfire based on engine speed signal, which boils down to the trigger wheel and sensor. If it's a little loose it could rattle around and give a false random misfire as the wheel bounces around.