How do you know your TB is "bad"? How is it defective?

From this section: http://www.grandprixforums.net/new-m...ads-36503.html

Very first link: http://www.grandprixforums.net/safel...car-17482.html

Here are a bunch of websites to get you guys started:

www.zzperformance.com
www.3800performance.com
www.intense-racing.com
www.tripleedgeperformance.com
www.getoverkilled.ca
http://home.comcast.net/~greenbastard/GBP/index.html
www.moradpartscompany.com
If you're stock, the N* TB is too big and not worth going from progressive to linear throttle style.