collector extensions and improved ET'S

I just want to see what everyones experiences have been with using collector extensions on the headers.

What have you found on the dyno or better yet on the race track?

Discuss any testing done using different lengths, or even using no collectors at all.

Just thought this could be very informative for all. Have heard many stories about what bolting on collector extensions can do for a car.

making your own is cheap, but even a set from Jegs is only around $40.

Lets hear your thoughts?