A few things,
Welcome to the VF.
Second there are a bunch of threads on this very subject. No less than 2 circulating recently. The search feature is your friend and likes to be used like a $2 hooker.
Third you cannot do the download yourself.
Fourth, you don't need a tuner unless you are planning on doing internal work to the engine.
I'm assuming by you member name you have an 07 Vegas.
The best download is the S&S 05 Hammer DRAG download.
This is a technical question and we have a forum especially for Technical issues. You have a netter chance of getting a quicker answer when you post in the correct forum. I will move this thread to that forum.
How is that for a welcome?