I didn’t think of the manifold leaks. I believe that could cause a lean condition if it’s drawing some air in rather than spitting it out - maybe changing with throttle as you’re seeing. I need to check this as well - my fuel trims are also running a little high, around 7% or so, but not causing any other symptoms yet. I think I recall you and Fuji4 both have had exhaust manifold bolts that snapped off. What’s the best way to get a look at that part of the exhaust manifold.