Pitstop issue

How can I reduce the pitstop timing apart from reducing to the minimum the values in the Pitstop Timing Configuration file in the gp4tweak_data?
I have many MODs with the same configuration in which the pitstop timing ranges from 6 to 8 seconds but am working on another MOD and in this one, the pitstop timing is about 15 seconds.
I tried everything but could not reduce the time, seems that the guy from the rear jack delays to release the car.