As already stated, power adjustment is a no-go subject to be discussed on open forum as the information can be used to make a normal, legal air rifle into an unregistered firearm in the eyes of the law.
I know you say you only want to do a little bit but consider these points:
1. If you do it and its not done right then you risk injury, damage or breaking the law - We, as a legitimate and responsible airgun community cannot be a party to providing the information that could cause any of these things.
2. You are a new member, asking for information on altering the power of an air rifle. Although you say here that you want to stay within the law - put yourself in our shoes - How do we know that you won't misuse the information given ???
Any person giving you such information could probably be prosecuted for aiding and abetting a criminal act (Not actually sure of this but with todays justice system
)
Please, do not take this reply as a personal dig at you as it isn't nor is it a slur on your self in any way, but as a responsible forum we will only advise you on issues that will keep you within the law and make you a valuable member of our forum.