Fuel trims

[anniversaryss]

What would cause long term fuel trims on one bank be significant higher compared to the other.
Example my car on old tune was running long term 25 percent (max)on passenger side driver was very little. This seems to occur at idle not as bad under throttle.
New (mail order) tune is about 15 to 19 on that side now.
Under throttle long term and short term trims 0 out
At idle short term trims between 5 and 10 maybe less but still more on that one side
I have idling issues it seems to idle fine in gear or park with some oscillation.
In drive when i come to a stop it wants to stall bit catches then levels out. Only stalled once