Is it possible to find out what has been changed when updating PCM calibration. We have had all kinds of different issues from shifting concerns to loss of fuel economy. Never have found to make vehicle run better but to fix an emissions issue and vehicle almost always runs different and costumer complains. I know we don't have a choice on some updates but if we could tell the customer what to expect then it would be better. Thanks for the help in advance.

Eric Newton
Shop Foreman/Technician
Curts Auto Repair
Phoenix, Arizona, USA