There are a few members that when they post. It might as well be written in stone. Here is a collection of posts to help new members get a look over some good data. I know there are several other great members here that can help add to this list or help give suggestions to this post.
Exhaust.
What your exhaust looks like and more
Motor 4.2 & RS4
http://audirevolution.net/forum/index.php?topic=67.0
http://audirevolution.net/forum/index.php?topic=85.0
http://audirevolution.net/forum/index.php?topic=82.0
http://audirevolution.net/forum/index.php?topic=100.0
http://audirevolution.net/forum/index.php?topic=66.0
http://audirevolution.net/forum/index.php?topic=106.0
Brakes
http://audirevolution.net/forum/index.php?topic=169.0
Drag strip Advice
http://audirevolution.net/forum/index.php?topic=521.0
How the B6 S4 stacks up performance wise.
http://audirevolution.net/forum/index.php?topic=1758.0