Rat patrol-
The comment made by lxmodguy is only specific to the Fact that EFI Source will provide you with a tune for a bone stock 6.1 and that's it. They won't help you with another tune, which is needed if you've upgraded the motor at all. His comment has nothing to do with the MS3x computer they use, as it is capable of anything and everything you would want to do. You could very well buy the EFI Source and follow my tuning advice in other posts and dial it in yourself, but mistakes could cost you a motor.
Further, as far as I can tell, the 'sales pitch' from lxmodguy is that you get a 'base tune' for your combo, whatever it may be (cam, heads, etc etc). And, he'll dial the tune in for a fee.