A mate sort of went through the same thing, he wasn't really happy with the power he got after a tune. He hadn't done valve springs though, so it made even less power. I suggest you do an apples to apples comparison. Load the stock tune (assuming you have a flash box), drive how you used to, change back. That's the only true way to see just how much of an improvement has been made. Be warned, with an X3, it will take a while to change tunes. Needless to say my mate did just that, reloaded his 10psi tune, and hasn't changed back yet.