I am looking into getting a tune and have decided on GH over LMS as most on here would agree its the better overall tune. However, on GH website it's $499 for the SCTx4 tuner which says it includes "3 tunes" which I have read includes the desired "Auto Octane" tune from GH. It offers the option to add a custom tune for $100. What benefit is there to the custom tune? Please help!