Found a good video on youtube that explains exactly what LTFT and STFT is and what causes it to change. Not Nistune specific but related.
Video is long so find a quiet place to watch it and pay attention. LOL
Alot of other good trouble shooting efi videos by the same poster (ScannerDanner)
https://www.youtube.com/watch?v=oRX2V6_a3dc
Good Fuel Trim (LTFT and STFT) explanation video
Moderator: Matt