Very high long term fuel trims

TheBoomSpoon

Does anyone have any ideas on how my Long term fuel trim's can be 28-30% on bank 1 and bank 2 but yet live monitoring of the AFR during tooling around town as well as WOT is well within spec. WOT throttle a bit on the rich side around 11.6 and tooling around generally flopping between 14.3 to 14.7. Completely off throttle is 29 which I assume is normal?

Monitor test for emissions show all systems good, I'm using ODBLINK software on my android phone to test for emissions as it runs the test to spec for each state's requirement and for MD I show ready for emissions so I think that is good. Obviously I'm throwing Codes for "system too lean" in P0174 and one other one is which is lean also.

I just can't rationalize in my brain how the real-time view of the AFR never gets out of line yet the long term fuel trim is so high, monitoring of the short-term trims seem to bounce around -5.6% and 6% which to me seems Ok nothing extreme but it puzzles me how if the short terms are never out of line by that huge amount how in the world can the long term trims be so bad?

anyway, anyone with any insights , I'm figuring a bad o2 should give outrageous for short term also.

Thanks
Kevin