I am looking for an interface to my car, for a maximum of 100 USD, it can be a little more expensive, but without exaggeration.
There are a lot of cheap interfaces from china, but I have no idea what to look for, they have different markings - year, version number, e.g. from 1.59 to 1.99, some have pic18f458. As for a novice user, there is too much of it and I do not know what to choose. What would I like to change in my car:
1. Capacity of the gas tank - now it is physically 58l, and it was 14l and the computer shows incorrectly the amount of fuel and range (cylinders from CNG are removed)
2. Change in the type of fuel from CNG to LPG in the computer - installation will be performed within 1-2 months.
3. Increase the number of displayed parameters by the computer.
4. Automatic folding of mirrors after closing the car and their unloading after inserting or turning the key.
5. Car diagnostics when something starts to go wrong.
The interface will only be for one car, so I do not want to spend a lot of money.

Will help someone with information, what model to choose, what to look for, what I can not do with this interface?
Will it be possible to make a copy, which can be restored if necessary?

HI