[Mach 1]

I would save your money on the driveshaft. I had one, and while it is a nice piece and not to expensive, there are better things you can do for the money to maybe give you better gains.

The main reason people run them is vibration problems, and if you arent experiencing them, you really wont gain anything from it.

I took mine off and sold it when I needed some cash. No performance difference whatsoever noticeable.